《孫子註解》Vol. 10

In Sunzi's Art of War: Terrain, it is stated that military campaigns require thorough examination of geographical features. Strategists like Cao Cao emphasized that before deployment, armies must scout the lay of mountains and rivers within a fifty-mile radius to detect ambushes. Commanders must personally survey the terrain, map it out, and understand its hazards and accessible routes to ensure victory.

Sunzi categorizes battlefield terrain into six fundamental types:

The first is "accessible terrain" (通形), referring to flat, open areas where both sides can move freely. Mei Yaochen explains this as terrain with interconnected roads, while Du You adds that movement is equally convenient for both sides on plains. When fighting in such terrain, one must seize sunny high ground first and secure supply routes. Cao Cao proposes the principle: "Better that I constrain the enemy than let the enemy constrain me." Li Quan advocates striking first, while Du Mu details the need to build fortresses or protected corridors at key crossings to safeguard supply lines. Jia Lin notes the importance of camping on elevated ground with clear visibility and logistical advantages.

The second is "entangling terrain" (挂形), which Mei Yaochen describes as a snare where advance and retreat become difficult. The third, "stalemate terrain" (支形), refers to standoff conditions where both sides are locked in confrontation. The fourth, "constricted terrain" (隘形), consists of narrow passages between mountains. The fifth, "precipitous terrain" (险形), involves hazardous landscapes like steep hills and gorges. The sixth, "distant terrain" (远形), covers far-flung flatlands. Du You concludes that mastery of these six terrains leads to victory, while Zhang Yu stresses that commanders must comprehensively grasp their characteristics.

This passage primarily discusses terrain utilization and tactical choices in military strategy. Mei Yaochen believed that in warfare, one should first occupy high ground and sunny positions while controlling crucial supply routes, thereby gaining advantage when the enemy attacks. Commentators like Wang Xi, He Shi, and Du You all agreed with this perspective. Zhang Yu supplemented that by seizing advantageous terrain first and awaiting the enemy, one could maintain the initiative, though precautions must be taken against the enemy refusing engagement—hence ensuring ample provisions is essential.

The "hanging terrain" (referring to terrain where advance is possible but retreat difficult) describes positions where forward movement is feasible but withdrawal problematic. Du You explained that "hanging" means being constrained or obstructed. When fighting in such terrain, if the enemy is unprepared, an attack can secure victory; but if the enemy is prepared and the attack fails, retreat becomes difficult, putting one’s own side at a disadvantage. Li Quan and Du Mu further elaborated that such terrain often consists of perilous, interlocking positions with the enemy—success requires striking unexpectedly. If the enemy is alert, they may exploit the terrain to cut off retreat routes. Chen Hao advised that when trapped in such terrain, preparations for prolonged warfare should be made, including seizing enemy provisions while awaiting opportunities.

The "branching terrain" (referring to deadlocked positions) describes situations where offensive actions are unfavorable for both sides. Du You explained that "branching" implies prolonged stalemate, where neither side benefits from extended standoffs. Zhang Yu noted that in such terrain, both sides occupy strategic positions that mutually constrain each other. Li Quan considered this terrain as disadvantageous as "hanging terrain," necessitating dispersed forces. Du Mu pointed out that in such mutually fortified positions, one should avoid initiating attacks outright; instead, feigning retreat to lure the enemy and counterattacking when half their forces are committed would be most advantageous.

When two armies face each other in a narrow, elongated stretch of flat terrain, deploying troops becomes difficult, and engaging the enemy often places one in a low-lying, disadvantageous position. Such terrain is unfavorable for both sides. In such situations, it is best to take the initiative to withdraw and set up an ambush. If the enemy pursues, the most advantageous moment to launch a surprise attack is when half their forces have passed through the treacherous section. If the enemy retreats first to lure our troops, we must not rashly give chase.

Ancient military strategists have analyzed this from different perspectives: Chen Hao believed that such terrain is complex and difficult to use—if the enemy feigns retreat as a lure, our army must not pursue. If our forces withdraw and the enemy halts their pursuit, we should let it be; if they attack, we should strike when half their troops have crossed. Jia Lin pointed out that such fragmented terrain is suitable for ambushes but not for initiating an attack first. Du You emphasized the need to discern the enemy's feigned retreat as a trap and counterattack only when they withdraw. Both Mei Yaochen and Wang Zhe advocated seizing strategic positions, setting ambushes to lure the enemy, and launching a surprise attack when half their forces have emerged. Zhang Yu specifically warned: when the enemy pretends to retreat, do not pursue; abandoning strategic terrain will leave one at the enemy's mercy—instead, actively withdraw to lure them into pursuit.

Regarding tactics for treacherous terrain (隘形, "narrow passes"): one should race to occupy and heavily guard the mountain pass (a narrow passage between two mountains), cutting off the enemy's advance and retreat routes. If the enemy has already seized the pass: do not force an attack if they have it heavily fortified; if their defenses are weak, then an assault may be feasible. Cao Cao elaborated: deploying troops at the pass allows for unexpected victories, but if the enemy has tightly sealed it, avoid confrontation; if they only control part of the pass, seize the initiative. Li Quan illustrated this with examples: the Zhao army's failure to hold Jingxing Pass allowed Han Xin to succeed, while Chen Xi's neglect of the Zhang River enabled Emperor Gaozu of Han to triumph—the key lies in fully exploiting the advantages of narrow-pass terrain.

This passage explains the ancient military strategist Sun Wu's key principles for utilizing terrain in warfare. Du Mu interprets "ying" (盈) as meaning "full" - when an army is positioned in a valley between two mountains, it must establish camp and deploy formations at the mountain pass, completely occupying the entrance like water filling a container to the brim.

Du You elaborates that this "level-mouthed full capacity" tactic resembles filling water precisely to a container's rim. By securing such strategic locations, one controls both flat and treacherous terrain, enabling surprise attacks against enemies. If adversaries only hold half of a pass without understanding this "full capacity" principle, our forces can advance through the gap. When both sides occupy precarious positions, victory depends on tactical skill rather than terrain alone.

This principle applies beyond mountain passes. In flat marshlands where chariots struggle and boats cannot pass, controlling the sole passageway can block enemy advancement. Chen Hao emphasizes the crucial importance of securing passes, while Jia Lin adds that well-defended positions shouldn't be assaulted directly, but vulnerable ones may be attacked.

Wang Xi and Zhang Yu both endorse this view, stressing the need to first occupy level valleys between high mountains, completely controlling passes to establish formations that prevent enemy progress. This allows our forces to launch surprise attacks while hindering enemy interference. If enemies first secure strategic positions with strong defenses, avoid direct confrontation; if their defenses show weaknesses, engage to contest the strategic terrain.

Wu Qi specifically warns against camping directly opposite "heaven's furnace" (the exit of large valleys), considering this a major military taboo. When fighting in treacherous terrain, always secure elevated, sun-facing positions to await battle with rested troops. Du You explains that holding high, sunny ground allows victory when enemies attack from lower, shaded positions. If enemies first occupy strategic terrain, withdraw rather than force an attack. Both Cao Cao and Li Quan emphasize never engaging passively in difficult terrain, while Du Mu points out that sheer mountain valleys cannot be altered by human effort - one must seize advantageous positions.

In military operations, if the enemy has already seized advantageous terrain, our side should not force a confrontation but instead take the initiative to withdraw. The "yang" position refers to open southern terrain—if the enemy occupies this yang position for an extended period while our forces remain in the yin position (northern exposure), we risk falling into passivity. For example, when encountering enemy troops in areas like Xiao Mountain or Mianchi, priority should be given to securing the northern high ground—a formation that relies on yin terrain while facing yang. When choosing between elevated positions and yang terrain, it is better to forsake yang and hold the high ground rather than abandon elevation to seize yang. This principle aligns precisely with Sun Tzu's teachings.

Du You notes: Seizing strategic terrain first prevents being controlled by others. Mei Yaochen adds: Controlling key positions early, occupying elevated yang-facing formations, and awaiting battle while rested ensures advantage; if the enemy has already secured such positions, reckless attacks will fail, and withdrawal is imperative. Wang Zhe illustrates with the Tang Emperor Taizong's preemptive control of Hulao Pass against Dou Jiande as a classic case. Zhang Yu further analyzes: Even on open plains, securing initiative is crucial—how much more so for strategic terrain? Occupying elevated yang positions while rested guarantees victory. If the enemy holds advantageous ground, rapid withdrawal is essential. He cites Pei Xingjian's campaign against the Turks: after encamping at dusk, Pei suddenly ordered relocation to higher ground. Though reluctant, his troops complied—only to witness a night storm flood their original camp under ten feet of water, proving that holding high ground offers both tactical superiority and protection against disasters.

Regarding "distant formations" (balanced situations where opposing forces are far apart): Cao Cao explains "provoking battle" means luring the enemy to attack. Li Quan observes that outcomes are unpredictable when strengths are matched. Du Mu illustrates with cases: marching thirty li to challenge a rested enemy is disadvantageous, and vice versa. The true solution is for both sides to advance, shortening the distance. Chen Hao concludes: When camps are distant and forces evenly matched, rash challenges inevitably fail—like attacking with one-tenth strength destined for defeat. He emphasizes assessing whether one's strength can overwhelm the enemy before challenging; otherwise, restraint is mandatory.

This passage discusses several scenarios leading to military defeat. When two armies are evenly matched, yet one attempts to attack with only one-tenth of the opposing force, this is called "flight" (走). Cao Cao explains this stems from overestimating one's capabilities, while Li Quan adds that such tactics could only succeed with advantageous terrain and surprise attacks. Du Mu elaborates that attacking one-to-ten odds requires tenfold superiority in all aspects; attempting this with equal strength inevitably leads to rout.

Mei Yaochen observes that engaging with vastly inferior numbers guarantees defeat and retreat, while Wang Zhe states such situations don't even warrant engagement—flight becomes inevitable. Zhang Yu concludes that when commanders' wisdom and soldiers' quality are comparable, initiating battle is already unwise, let alone fighting outnumbered—how could this not end in retreat?

Another failure called "slackness" (弛) occurs when troops are strong but officers weak. Jia Lin notes these defeats all stem from human mismanagement rather than unavoidable circumstances. Zhang Yu emphasizes all six defeat patterns originate from human error, not natural disasters.

These terrain principles constitute a commander's paramount responsibility. Li Quan warns that commanders ignorant of these will surely fail, while Jia Lin states terrain advantages can be intuitively assessed. Mei Yaochen stresses terrain as fundamental to victory, and Zhang Yu insists commanders must master these six terrain characteristics.

The commentaries collectively demonstrate: rashly attacking with inferior numbers against equal opponents guarantees failure, commanders must act according to actual capabilities, and officer-soldier dynamics require careful management—these form the essential principles of military command.

This passage presents ancient military strategists' annotations on two key concepts from The Art of War: "when officers are strong but soldiers weak, this is called collapse" and "when subordinate commanders rage insubordinately." Multiple strategists interpret these as scenarios of military failure caused by poor management.

The first situation, "officers strong but soldiers weak," describes cases where commanders are formidable but their troops lack courage. Cao Cao notes that if such leaders press forward aggressively, it will lead to disaster. Li Quan adds that when soldiers are of uneven quality, they become unreliable in battle. Du Mu argues that this kind of defeat stems from forcing an attack without considering the actual capabilities of the troops. Chen Hao analyzes it from a training perspective: if commanders lack leadership skills and soldiers are poorly drilled, the entire unit loses combat effectiveness. Multiple commentators emphasize that a commander’s personal bravery cannot compensate for weak soldiers—pushing forward recklessly will only result in total annihilation.

The second situation, "subordinate commanders rage insubordinately," refers to mid-level officers (大吏, dali) defying their general’s orders. Cao Cao explains this as lower-ranking officers acting out of anger, disregarding the larger strategy and engaging in battle without authorization. Li Quan vividly describes this breakdown in command structure with the term "collapse" (崩, beng). The annotators unanimously agree that when officers harbor resentment and act independently while the commander fails to maintain control, the army will disintegrate like a landslide.

The text also cites two historical examples: during the Tang Dynasty, Tian Bu’s lack of authority over the Weizhou troops led to their disintegration; and during the Spring and Autumn period, Prince Guang of Wu predicted the defeat of the Chu army due to chaotic governance and incompetent leadership. These cases reinforce the military principles discussed above.

This scripture passage explains how a commander who is provoked by the enemy and drives his troops into battle without considering their actual strength will inevitably lead to military collapse. Du Mu cites a historical case from the Spring and Autumn period to illustrate this: when the state of Chu attacked Zheng, the state of Jin sent troops to aid Zheng. The Jin army suffered from severe internal issues—the newly appointed commander lacked authority, the deputy commander Xian Hu was stubborn and arrogant, the three main generals acted independently without coordination, and the soldiers were left confused and directionless. To make matters worse, two disgruntled officers, Wei Qi and Zhao Zhan, took reckless actions due to their personal grievances. Although Sui Hui advised setting up defenses, Xian Hu obstinately refused, ultimately resulting in the crushing defeat of the central and rear armies (only the forward army, which had prepared seven ambush positions in advance, managed to survive unscathed).

Commentators analyze this case from different perspectives: Chen Hao points out that the commander’s unreasonable anger provoked resentment among his subordinates, leading them to act rashly in battle; Jia Lin uses the term "collapse" (崩) to describe this top-down disintegration, emphasizing that a commander who disregards his troops’ capabilities and forces them into reckless combat is courting disaster; Mei Yaochen and Wang Xi both argue that the root problem lies in the commander’s failure to understand his subordinates’ abilities, using misguided methods that only fuel discontent; He Shi and Zhang Yu conclude that victory requires unity of purpose—if commanders harbor mutual resentment and rush into battle impulsively, defeat is inevitable. The passage also references another historical example involving Xun Yan of Jin, who arrogantly ordered, "We march at cockcrow—follow my lead alone," provoking strong opposition from Luan Shu, who retorted, "The fate of Jin should not be decided this way"—further illustrating the disastrous consequences of a commander’s tyranny.

(Note: "Challenging the enemy" (致师) refers to an ancient ritual of provocation; "requesting a mission" (请使) means volunteering for an envoy role; "seven ambushes" (七覆) indicates seven hidden positions; "royal clan officers" (公族) denotes officials from the ruling family lineage.)

This passage discusses the chaos that arises when military leaders fail to properly command their troops. If a general is weak and incompetent, with lax discipline and disorganized training, officers and soldiers will become undisciplined, forming sloppy battle formations—this is the manifestation of "disorder." Commentators like Cao Cao have noted that when commanders lack authority, employ ineffective training methods, make frequent personnel changes, and face disobedient troops, they are courting their own defeat.

The text further explains how failure to accurately assess enemy situations—such as deploying small forces against large armies, attacking strong positions with weak ones, or neglecting to select elite troops—inevitably leads to defeat. Historical commentaries provide examples: Li Jing's military treatise emphasizes selecting dare-to-die squads as vanguards, while Eastern Jin general Xie Xuan famously organized the elite "Beifu Army." These successes stemmed from carefully choosing the bravest soldiers. Generals who fail to select elite troops or distinguish between strong and weak soldiers are marching toward destruction. As Mei Yaochen summarizes: misjudging the balance of power between enemy and allied forces guarantees defeat.

(Note: The Beifu Army was an elite unit established by Xie Xuan during the Eastern Jin dynasty. Stationed at Jingkou (modern Zhenjiang), it earned the name "Beifu" [Northern Garrison] and became renowned for its exceptional combat prowess.)

This passage primarily discusses the causes of military defeat and the importance of terrain in warfare.

Regarding military failures, the text outlines six key scenarios: First, failing to assess troop numbers (not measuring strength); second, lacking discipline and reward systems (deficient in punishments and Virtue [De]); third, inadequate training (neglecting drills); fourth, commanders losing temper without cause (unreasonable outbursts of anger); fifth, failure to enforce military orders (laws and commands not implemented); and sixth, not selecting elite soldiers (failing to choose the bravest and most capable). These are all critical factors leading to defeat.

The text particularly emphasizes the importance of selecting elite troops. Historically, the Qi state relied on "skilled strikers," Wei on "martial warriors," and Qin on "sharp soldiers" to achieve victory. The Han dynasty had "heroes from the Three Rivers" and "swordsmen of extraordinary talent," Wu called their elite troops "trouble-solvers," Qi named theirs "life-deciders," while the Tang dynasty referred to them as "shock troops." Though the names differ, all denote rigorously selected elite forces. The text recommends choosing one soldier out of every ten, forming a special unit of a thousand from ten thousand, to be commanded by trusted generals.

Historical examples are cited: Cao Cao used Zhang Liao as vanguard to defeat the Xianbei, while Xie Xuan dispatched Liu Laozhi to lead elite troops against Fu Jian—both illustrating the decisive role of crack forces. Attempting to attack larger forces or confront stronger enemies without elite vanguards inevitably leads to defeat.

Concerning terrain, the text identifies it as a crucial auxiliary factor in warfare (an aid to soldiers). Although the foundation of war lies in humaneness and discipline (the essence of war rests in humaneness and regulation), occupying advantageous terrain can secure victory. Quoting the ancient saying, "Heaven's timing is less important than Earth's advantages," the text underscores terrain's significance while also noting that "terrain's advantage depends on human utilization"—meaning geographical benefits still require proper exploitation by commanders.

This passage discusses the fundamental principles of military strategy. It begins by emphasizing terrain's critical role in warfare: mountains can block enemy advances, water currents can submerge opposing forces, higher ground holds advantage over lower positions, and strategically difficult terrain surpasses open plains. However, Wang Xi stresses that the true decisive factor in warfare remains human agency. Zhang Yu supplements this by noting that while understanding terrain provides tactical support, the essential foundation lies in accurately assessing enemy situations and formulating winning strategies.

The discussion then shifts to a general's responsibilities. Du Mu asserts that commanders must calculate provisions consumption, soldiers' physical endurance, and the relative advantages of offense versus defense—all factors intrinsically connected to terrain obstacles and distance considerations. Wang Xi maintains that generals must thoroughly comprehend both enemy intelligence and the strategic advantages or disadvantages of the terrain. He Shi observes that understanding both the enemy and the battlefield constitutes a general's fundamental duty. Zhang Yu synthesizes these views, concluding that only by mastering both the enemy's actual conditions (strengths and weaknesses) and the terrain's strategic challenges (both obstacles and distances) can one fully grasp the art of generalship.

The text then underscores the vital importance of unifying knowledge with action: applying these principles in battle leads to victory, while ignorance of them results in defeat. Mei Yaochen states that commanders must understand both terrain and military administration. Zhang Yu elaborates further, explaining that only through simultaneous comprehension of enemy situations and geographical advantages can victory be achieved.

Finally, the passage examines the principle that generals in the field may sometimes disregard sovereign's orders. Li Quan asserts that battles should be fought only when aligned with the path to victory, and avoided when contrary to it. Du Mu quotes the Yellow Stone Patriarch (Huang Shigong) to illustrate that rulers should delegate full authority to their generals. Meng's commentary advocates prioritizing soldiers' morale over blind obedience to royal commands. Both Mei Yaochen and Zhang Yu emphasize that generals must decide whether to follow imperial orders based on actual battlefield conditions—better to achieve victory through appropriate disobedience than to incur defeat through rigid compliance. As the ancient saying goes: "In the army, only the general's orders are heeded; imperial decrees go unasked." A true commander should neither covet military glory nor shirk responsibility.

Wang Xi states that generals should serve their country with utmost loyalty. He Shi elaborates that when generals advance into battle, it is not for personal fame but because they see benefit for the state and its people; when they retreat, it is not to avoid blame but because they recognize how warfare would harm the nation and bring suffering to the populace. Even if the sovereign orders an attack, the general should refuse to comply—remaining unrepentant even if punished for disobedience.

Truly exceptional generals base all decisions on protecting soldiers and civilians while upholding the ruler's fundamental interests. Such commanders are national treasures. Li Quan explains that a general's tactical decisions must prioritize safeguarding the people over personal gain. Du Mu further clarifies that such generals neither covet hollow victory titles when advancing nor fear accusations of defying orders when retreating—such individuals are exceedingly rare. Chen Hao interprets "alignment" (合) as returning to fundamental principles. Mei Yaochen emphasizes it's better to disobey misguided commands and achieve victory than blindly obey and court defeat. Wang Xi concludes there's only one criterion for engaging in battle: whether it protects the populace and serves the ruler's long-term interests. Zhang Yu notes that when generals defy sovereigns, it's never for self-interest but to preserve lives and uphold the state's foundational welfare—this constitutes true ministerial loyalty.

Treat soldiers with infant-like care, and they will follow you through deadly terrain; cherish them as your own children, and they will stand with you in life and death. Li Quan cites how a single compassionate remark from King Zhuang of Chu warmed his entire army like winter clothing. Du Mu recounts the legendary general Wu Qi from the Warring States period: he ate the same food as low-ranking soldiers, marched on foot carrying provisions, and even sucked pus from a soldier's ulcer. When the soldier's mother heard this, she wept bitterly, explaining that Wu Qi had done the same for her husband—who soon died in battle—and now feared her son would meet the same fate. Mei Yaochen analyzes that genuine care from commanders inspires absolute loyalty in troops. Wang Xi advocates using benevolent compassion to forge unbreakable morale. He Shi cites Eastern Han general Duan Jiong, who spent over a decade on the frontier personally dressing wounds, never sleeping apart from his men, sharing all hardships—thus making soldiers willing to die for him.

This passage elucidates the proper relationship between generals and soldiers through historical anecdotes and military treatises.

When Wang Jun, the renowned Western Jin general, served as governor of Ba Commandery, the war-torn region saw families reluctant to raise sons due to constant conflict. Wang implemented strict decrees to reduce corvée labor while offering preferential treatment to childbearing households, saving thousands of lives. During the later Wu campaign, these rescued youths volunteered as soldiers, with parents admonishing them: "Governor Wang gave you life—you must repay him with loyal service unto death." This demonstrates how soldiers regard paternalistic commanders as father figures.

Ancient military strategists emphasized that only when officers care for troops like their own children will soldiers serve them with filial devotion. As Xunzi noted, subordinates should serve superiors with the same loyalty as children honoring parents or limbs protecting the head. The tradition of sharing fine wine with the entire army or inspiring troops with kind words has been celebrated throughout history.

Military classics record that exemplary generals must lead from the front—eschewing parasols in summer, extra layers in winter, and riding horses only after dangerous paths are cleared on foot. They drink only after soldiers dig wells, eat only when meals are cooked for all, and rest only when barracks are built. Yet overindulgence must be avoided, lest troops become as unruly as spoiled children.

Cao Cao warned that authority and benevolence must be balanced—exclusive kindness breeds waywardness like pampered offspring. Li Quan added that excessive coddling fosters rebelliousness, while Du Mu cited the Yellow Stone Patriarch's advice: "Be cordial yet never indulgent, cultivating morale through benevolence while enforcing discipline." The Yinfu Jing cautions that "excessive kindness becomes calamity."

Wu Qi asserted that battle drums and gongs awe the ears, banners and insignia command the eyes, while prohibitions and punishments discipline the heart. When hearing is awed by sound, soldiers stay alert; when vision is commanded by colors, they remain focused; when hearts are disciplined by law, they maintain order. Without these three, defeat is inevitable. Thus when great generals command, none disobey; where they point, troops charge without hesitation.

Li Jing concluded that ancient master strategists understood sacrificing one-tenth to preserve the whole—not cruelty, but the ultimate compassion.

This passage explains the principle of balancing kindness and authority in military leadership. A commander must establish both威严 (wei, authority) and恩惠 (en, benevolence), applying them in measured harmony.

Regarding威严 (authority), consider the methods of ancient generals: Zhuge Liang wept while executing Ma Su for his defeat; Lü Meng tearfully enforced military law when a fellow villager stole a bamboo hat; Cao Cao cut off his hair in place of his head when his warhorse trampled crops. Though seemingly harsh, these acts demonstrated restraint of personal sentiment in upholding discipline, enabling small forces to achieve maximum effectiveness. Conversely, excessive indulgence toward troops leads to certain defeat, regardless of numbers.

On the interplay of恩惠 (benevolence) and威严 (authority): if a leader only shows kindness, punishments will breed resentment; if only severity is used, benevolence becomes meaningless once hatred takes root. The principle mirrors the Yi Jing's师卦 (Shi Gua, "Army" hexagram): the初六 (first line) stresses strict discipline ("an army must set forth with firm rules"), while the九二 (second line) emphasizes timely rewards ("the general receives Heaven's favor"). History's great commanders understood this—Wu Qi sharing food and clothing with his soldiers, or He Lü laboring alongside his troops, exemplified benevolence; Li Jing's ruthlessness in executing every third offender demonstrated authority.

As the strategist Wei Liaozi observed: troops will not serve a commander they do not genuinely love, nor obey one they do not deeply respect. Thus, the art of leadership lies in calibrating the balance between "affection" and "awe."

A final insight on military judgment: knowing only your own strength while ignoring the enemy's invincibility grants merely a fifty percent chance of victory. This reminds commanders to assess both their own capabilities and the adversary's condition with equal clarity.

Mei Yaochen said: To know oneself but not the enemy may occasionally bring victory; to recognize the enemy's vulnerability without assessing one's own army's readiness offers only half the chance of success.

Du Mu explained that "vulnerability" refers to an enemy being reckless and underestimating their opponent, while "invulnerability" means the enemy is exhausted and demoralized. Chen Hao refuted this, arguing that the true determinant lies in comparing the relative strength of forces, the discipline of soldiers, and the rigor of reward and punishment systems.

Wang Xi pointed out: Neither knowing only oneself nor knowing only the enemy guarantees victory. Zhang Yu added that both one-sided perspectives make outcomes uncertain. Emperor Taizong of Tang once shared his experience: Before every battle, he would first assess whose strategic planning was more thorough, observe whose morale was higher, and analyze psychological states and military momentum to determine relative strength before deciding whether to engage.

Knowing the enemy can be attacked and one's own army is capable, yet failing to understand whether the terrain is suitable for battle still yields only half the chance of success. Cao Cao and Li Quan interpreted "half-victory" as an uncertain outcome. Du Mu emphasized that terrain encompasses factors like difficulty and ease, distance, and routes of advance and retreat. Mei Yaochen noted that even with full awareness of both sides, unfamiliarity with terrain could lead to defeat. Wang Xi added that even with favorable conditions, one must not overlook the advantage of terrain. Zhang Yu concluded: Even knowing both oneself and the enemy, without the aid of terrain, complete victory remains unattainable.

A true master of warfare acts without confusion and makes decisions without falling into difficulty. Du Mu explained that such a commander determines victory or defeat before taking action, thus remaining unshaken in execution and unhindered in strategy. Chen Hao stated that "difficulty" refers to being trapped—if one accurately assesses the dynamics of both sides and the advantages of terrain, they can advance or retreat freely and fight without peril. Mei Yaochen believed that comprehensive understanding prevents disorientation. Wang Xi noted that those skilled in planning do not waver, and those adept at managing armies do not falter. Zhang Yu summarized: Acting without haste ensures precision, and deliberating before decisions ensures appropriateness.

In military operations, victory can only be achieved by first assessing the relative strengths and weaknesses of both sides while securing advantageous terrain. This principle underlies the saying: "Know the enemy and know yourself, and you shall never be defeated in a hundred battles."

Zhang Yu explains: Understanding the tactical essentials of offense and defense ensures victory without peril. Li Quan adds: Mastery of three factors—human affairs (troop conditions), celestial timing (climatic conditions), and terrestrial advantages (topographic superiority)—guarantees triumph in every engagement. Du You elaborates: Terrestrial advantage means occupying strategic positions and choosing sunlit high ground; celestial timing involves adapting to seasonal changes and following natural patterns.

Mei Yaochen observes: Recognizing both the enemy's strengths and one's own advantages prevents peril; comprehending celestial variations while mastering terrain characteristics averts desperate situations. Wang Xi concurs with Mei's view. Zhang Yu concludes: Aligning with celestial timing and securing terrestrial advantage yields inexhaustible victories.

(Note: This passage presents classical military commentators' annotations on Sunzi's principle "Know the enemy and know yourself, and you shall never be defeated in a hundred battles," emphasizing comprehensive consideration of combatant conditions, weather patterns, and geographic factors for military success.)