Original Text
Sun Tzu said: There are six types of terrain: "accessible," "entangling," "temporary," "narrow," "precipitous," and "distant." Ground that both we and the enemy can traverse is called "accessible." On accessible terrain, take the high, sunny positions first, keep your supply routes open, and you will have an advantage. Ground that is easy to advance into but hard to retreat from is called "entangling." On entangling terrain, if the enemy is unprepared, you can strike and win; if they are prepared and you cannot win, retreat becomes difficult, and this terrain becomes unfavorable. Ground that is disadvantageous for both sides to attack is called "temporary." On temporary terrain, even if the enemy offers a bait, do not advance. Instead, feign retreat, lure the enemy halfway, then turn and strike—this will be advantageous. On narrow terrain, you should occupy it first and seal the pass with strong forces, waiting for the enemy. If the enemy occupies it first and blocks the pass heavily, do not attack; if they do not guard it heavily, you may still attack. On precipitous terrain, if you occupy it first, control the high, sunny positions and await the enemy. If the enemy has already taken the advantageous positions, withdraw and do not attack. On distant terrain, when both sides are evenly matched, it is unfavorable to provoke battle; forcing an engagement will bring disadvantage. These six principles are the keys to using terrain. They are the general's greatest responsibility and must be carefully studied.
There are six types of military defeat: "flight," "laxity," "collapse," "disintegration," "disorder," and "rout." These six conditions do not arise from natural factors like weather or terrain, but from the faults of the commanding general. When both sides are evenly matched, yet one attacks ten times the enemy's strength and fails, it is called "flight." When soldiers are strong but officers are weak and command poorly, leading to defeat, it is called "laxity." When officers are strong but soldiers are cowardly and lack combat effectiveness, causing defeat, it is called "collapse." When subordinate commanders harbor grudges and refuse to obey orders, engaging the enemy on their own initiative without the general's knowledge of their abilities, resulting in defeat, it is called "disintegration." When the general is weak and lacks authority, the army is poorly disciplined, relations between officers and men are strained, and battle formations are chaotic, leading to defeat, it is called "disorder." When the general fails to correctly assess the enemy, attacks a larger force with a smaller one, a stronger force with a weaker one, and lacks elite vanguard troops, resulting in defeat, it is called "rout." These six conditions are all inevitable causes of military failure. They represent the general's grave responsibility and must be carefully examined and studied.
Terrain is a crucial aid in military operations. Correctly assessing the enemy, seizing the initiative for victory, evaluating the ease or difficulty of the terrain, and calculating distances—these are principles and rules that a wise commander must understand and master. Applying these insights to command ensures victory; failing to do so ensures defeat.
Therefore, according to the general principles of warfare, if there is certainty of victory, the commander may insist on engaging even if the ruler forbids it; if analysis shows no certainty of victory, the commander must refuse to fight even if the ruler insists. Thus, as a general, one advances not for the name of victory, retreats without fear of blame for defeat, but only seeks to protect the people and serve the nation's interests. Such a commander is a true treasure of the state.
Treat soldiers as tenderly as infants, and they will share hardships with their commander; care for them as beloved sons, and they will stand by their commander through life and death. If you indulge them without enforcing discipline, treat them generously without putting them to use, or allow them to break rules without punishment, they become like spoiled children—unfit for battle.
Knowing only your own forces but not the enemy's situation gives you only half a chance of victory. Knowing only the enemy's situation but not your own forces also gives you only half a chance. Knowing both the enemy and your own forces, yet not understanding that the terrain is unfavorable for battle, likewise gives you only half a chance. Therefore, a commander who truly understands the art of war acts without confusion and employs tactics that are endlessly adaptable.
Thus it is said: Know the enemy and know yourself, and you can win every battle. If you also understand the heavens above and the terrain below, your victory will be complete and without flaw.
Commentary
Terrain is an objective condition frequently encountered in warfare. Its complexity and variability require military commanders to conduct thorough reconnaissance, while also understanding the situation of enemy troops and their leaders, determining battle plans accordingly. Sometimes terrain appears simple, yet the enemy may have set an ambush; other times terrain is complex, but with meticulous planning, victory can still be achieved.
Example Interpretation
The Phantom U-Boats of the Mediterranean
Since the 19th century, the Strait of Gibraltar, less than seven miles wide, has served as a critical choke point between the Atlantic and the Mediterranean, and has been controlled by the British, who once called their empire the one on which the sun never sets. After the outbreak of World War II, the Italian Navy under Mussolini clashed with the British Navy in the Mediterranean several times, only to be repeatedly routed. Mussolini repeatedly begged Hitler for help, requesting that the "wolves" of the German Navy—U-boats—enter the Mediterranean to attack British warships. However, the British had long anticipated this move. To set a trap and seal the enemy's fate, they stationed heavy forces at Gibraltar, with a dense array of radar, sonar, and anti-submarine destroyers tightly blockading the strait. Any German submarine approaching the strait would be immediately detected. Yet, a strange phenomenon occurred:
On November 3, 1941, the Royal Navy's aircraft carrier HMS Ark Royal was sunk in the Eastern Mediterranean by the German submarine U-81 with three torpedoes. Of the over 900 crew members, only one survived. That same month, the battleship HMS Malaya was also damaged by a German submarine.
On June 5, 1942, HMS Barham, one of the largest British warships in the Mediterranean—displacing nearly 40,000 tons and armed with eight 15-inch guns—was sunk by German submarine U-331, 30 nautical miles off the Libyan coast, killing 863 British personnel. A month later, U-331 safely arrived at the submarine base in La Rochelle, France, to replenish its ammunition.
On August 11, 1942, the Royal Navy aircraft carrier HMS Eagle was sunk by U-73 southwest of the island of Malta, killing over 330 people.
……
The relentless attacks and heavy losses shocked the British forces: German U-boats had entered the Mediterranean undetected, moving almost with complete freedom, rendering the blockade of the Strait of Gibraltar virtually useless!
So, how did German submarines enter the Mediterranean? It turns out that German U-boat captains made full use of the ocean currents in the Strait of Gibraltar area. Between the Atlantic and the Mediterranean on either side of the strait, differences in evaporation and density create two currents: on the surface, because evaporation in the Mediterranean is much higher than in the Atlantic, the sea level of the Mediterranean is lower than that of the Atlantic, forming a surface current that flows eastward from the Atlantic into the Mediterranean. At deeper levels, due to the higher density of Mediterranean seawater compared to the Atlantic, a deep current flows in the opposite direction. Thus, when cunning U-boat captains arrived near Gibraltar under the cover of night, they ordered the submarine's engines shut down, dove to a depth of 10 to 20 meters, and were carried into the Mediterranean by the surface current like fish. Without the roar of engines, British radar and sonar could not detect the submarines at all—truly stealthy and unnoticed. When they completed their mission and needed to exit the Mediterranean, they dove to 150 meters and, using the same method, were carried back out of the Mediterranean by the deep current.
The Battle of Taobao Forest
In the 1st century BC, Caesar's conquest of Gaul (present-day France) brought the Germanic peoples into direct contact with the Roman Empire as neighbors. Yet these two neighbors were not on friendly terms, and conflicts between them were constant. At the height of its power, the Roman Empire spent the following decades launching repeated campaigns against the unruly and barbaric Germanic tribes on the right bank of the Rhine. By the time of Emperor Augustus (Octavian, Caesar's adopted son), progress was finally made. Intimidated by the formidable might of the Roman legions, many Germanic tribes began to express submission. The Roman Empire's conquest of the right bank of the Rhine seemed imminent.
However, the fierce Germanic tribes had no intention of submitting. Hermann, the chieftain of the Cherusci tribe—a bold and cunning Germanic leader—won the trust of Varus, the Roman governor of Germania, by feigning compliance. He then secretly ordered a Germanic tribe to rise in rebellion. Enraged by the news, Varus led all three of his elite Roman legions to suppress the revolt, appointing Hermann as his guide. Seeing that Varus had fallen into the trap, Hermann led the Roman legions into the pre-set ambush—the Teutoburg Forest.
The Teutoburg Forest is a lowland area located at the border of present-day Lower Saxony and North Rhine-Westphalia in Germany. It is crisscrossed by river valleys, with highly undulating terrain, and most paths wind through gorges. Here, tall and dense oak forests grow with few shrubs, and sunlight struggles to penetrate the thick leaves to reach the ground. Behind the gloomy, dense woods and along the muddy, narrow gorges, Hermann ambushed a large number of ragged but robust Germanic warriors. When the Romans entered the forest, their initial march route was relatively flat and wide, but gradually the terrain began to rise and fall, and swamps spread everywhere, making every step a struggle for the Romans. As the road grew narrower and muddier, Varus's army, entering the great gorge, stretched out longer and longer. Just as the army was exhausted, a deep horn sounded, and the Germanic attack began. Countless arrows and sling stones shot from the woods along the road and from behind the rocks on both sides of the gorge, and the unprepared Roman soldiers fell one after another.
Although the Roman legions were well-equipped and highly disciplined, they did not panic after the sudden ambush. They quickly raised their shields and tightened their formation, attempting to form a battle square to face the enemy. However, the narrow road offered no space for any of their usual combat formations. As they fought and retreated toward the exit of the great canyon, they discovered in despair that the canyon mouth had already been blocked by hundreds of thick tree trunks, leaving only a narrow path wide enough for two people to walk side by side. Chaos inevitably erupted, and Roman soldiers began scrambling to flee for their lives. Seeing that the moment had come, Hermann ordered a full assault. With a thunderous roar, the Germanic tribesmen burst out of the forest like a mountain torrent. Hermann, leading a band of warriors wielding broadswords, charged at the very front.
In this battle, three elite units of the Roman legion were completely annihilated, with over 20,000 lives lost, including Governor Valens. Afterward, the Roman Empire could no longer cross the right bank of the Rhine, and the Germanic people finally broke free from Roman shackles to gain independence.