On War

In the realm of defense, “numbers, in general, cannot come under consideration” (217). The “three principles of victory” are: attacking from several directions, surprise, and the advantage of controlling ground (271). The latter ranges from natural obstacles to simply being acquainted with the area: “The assistance of ground” usually translates into “a greater influence than ever” on warfare (219). The attacker can only surprise once, but the defense may do so repeatedly. Clausewitz believes that reconnaissance of defensive positions may sometimes be impossible. At the same time, the defender is in a fixed position, while the attacker is mobile.

Clausewitz argues that “[i]n strategy there is no victory” (219). However, tactical victories have strategic success backing them and making further use of them. Overall efficient action in the realm of strategy comprises six key points: 1) ground advantage; 2) the element of surprise; 3) attacking from several quarters; 4) obstacles and fortresses in the theater of war; 5) people’s support; 6) psychological factors. The defense side benefits from surprise positions to meet the enemy in one’s own theater of war and from the advantage of the ground. The people’s support may vary depending on the geographic location.

Clausewitz treats attack and defense as “pure abstractions” (222). The defense must be waiting, while the attacker moves. The latter’s freedom of movement pertains to tactics but not to the realm of strategy. The advantages of action in tactics include using crossfire within a range, attacking the same point from different sides, and cutting off the ability to retreat. However, “we must conquer before we can think of cutting off an enemy’s retreat” (223). Clausewitz argues that “[t]he advantage of interior lines increases with the distance to which these lines relate” (223).

Defense is “a stronger form of carrying on war” (224), which may eventually turn to offensive actions and acquire victory. The defense must be prepared for war in every possible way—from a trained army to the loyal people—to avoid surprises if a conqueror is seeking to attack one’s country. Whichever side is ready first will “go to work offensively” (225).

The defense has multiple advantages, including the people’s militia, fortresses, the people, general mobilization, and allies. The militia (Landwehr) has a close relationship with the concept of defense. Such a militia may offer physical and psychological support to the regular army when there is “the whole mass of people in support of the war” (226). Fortresses help withstand sieges. If the general population voluntarily supports the war effort, then that is an additional advantage in contrast to the assailant, who forces the locals into cooperation. General mobilization will similarly support the defense. The allies are those who are “essentially interested in maintaining the integrity of the country” (227), have many shared interests, and seek to maintain a balance of power in Europe.

In general terms, war does not begin with an offensive, but rather with “taking possession of something” (229). It is the latter that generates defensive actions. Consequently, it is the defender “who first brings the element of war into action” (230). It is the defender that presupposes the existence of two sides in a war.

Defense is focused on warding off and on an expectation of attack. However, this is a relative, rather than an absolute state, as “[a] defence of the country,” Clausewitz argues, “only waits for attack on the country” (231). The same applies to the defense of an entire theater of war or a single position. Thus, the defense component comprises “two heterogenous parts, the state of expectancy and that of action” (231). In this context, defense is “the more powerful form of making war; in order to overcome the enemy more easily” (232).

The defense may act by attacking the assailant upon entry into the theater of war and by establishing a position close to where an enemy might appear in an attempt to attack. The defending side may also transfer its defense into the center of the country or put its army in a position “waiting to be actually assaulted” (232). In all these cases, the defense side “has the benefit of the ground or country” (233). Ultimately, “the aggressor is ruined by “the sword of the defensive, or by his own efforts” (235). In this context, the relationship between strategy and tactics is such that “every strategic combination rests only upon the tactical results” (237).

As the enemy invades, the defender attacks him using a battle “of a purely offensive character” (240). In strategy, a field of battle is only a point, its duration a moment in time, and the result “a strategic quantity” (240). For example, the defender may wait for an attack and, by relying on parallel trenches, “with a small part of his force to destroy great numbers of the enemy at every stage of the defence up to the heart of the position” (241). Clausewitz provides several other demonstrations of how the defender may optimize his situation by waiting until most of the enemy troops are in action and responding with “a smaller offensive battle on his own part” (241). However, the envelopment tactic of obtaining objectives in the enemy’s rear is dangerous in defensive battles because it limits retreat options. Overall, victory in defense is “more probable” in relation to “the total result of all the combats” as well as specific battles (243).

The initial purpose of building fortresses and similar structures was “the defence and protection of the inhabitants” of a town (243). Despite their diminished construction to protect towns, they remain effective and comprise an active and passive element. The active element allows attacks on an approaching assailant, while the passive counterpart provides safety and shelter.

Overall, “fortresses are great and most important supports of the defensive” (245). They can be used for storage and protection of towns. They act as barriers to rivers or roads. Fortresses may play the role of points d’appui (assembly points for the troops; See: Index of Terms) for tactical reasons. They may be a stopping point on a communication line. Fortresses protect wounded, weak, defeated troops. They are “a real shield against the enemy’s aggression” (246). They offer additional protection for cantonments. Fortresses may cover an unoccupied province. They may be “the focus of a general arming of the nation” with munitions and supplies (248). Finally, they can be used for the defense of mountains and rivers.

Different types of circumstances affect fortresses. First, defense fortifications should be established where “the most natural point of attack is situated” (250). Second, fortresses and fortifications may be located on a frontier, but there are exceptions to this rule, such as fortifying the capital city. Groups of fortifications give an army strength. The location of the fortification in terms of topography may differ. For example, if being located directly on the river is impossible, then fortifications should be built within 10 miles of it (252).

A defensive position is “[e]very position in which we accept battle, at the same time making use of the ground as a means of protection” (252). The term “defensive position” is typically connected with tactics. Defensive positions have four key strategic properties. First, such positions cannot be passed around. Second, the defender benefits from “the struggle for the lines of communication” (254). Third, the lines of communication may affect the combat form. Finally, the defense position has a positive impact on the country. For example, a defensive position “must particularly seek for the advantage of being able to overlook [one’s] adversary” (254). Also, if some features of this defensive position cannot be assailed, then the latter serves as an additional advantage.

A position “strong through nature” and “assisted by art” may be “unassailable” and is thus defined as a “strong position” (256). For example, such a position may use entrenchments—an art—in a naturally advantageous place. The three types are strong lines, strong positions, and entrenched camps located next to fortresses. On their own, lines are “simply worthless,” reduce defense mobility, and present little of an obstacle to the assailant (257). However, modern warfare retains them because of “the low degree of energy impressed on the conduct of war” and by using them as a “secondary defense against irregular incursions” (257-8).

Clausewitz describes positions as “the defence of a tract of country […] as long as the force designated for it maintains itself there” (258). Strong positions, therefore, are those that keep the rear safe, allow the defender to expect relief, and where the enemy force is not strong enough. Entrenched camps near a fortress may feature certain aspects that makes the siege difficult. Such camps may house a small number of troops and be used for assembly. Strong positions are particularly important in confined spaces, like small countries with little space for retreat.

A flank position is “[e]very position to be held, even if the enemy passes by it” if it allows addressing “the enemy’s strategic flank” (261). Unassailable positions are also advantageous whether or not the opponent passes by it. Overall, flank positions are extremely effective especially when they use “a small expenditure of force” (262).

Mountains leave a significant impact on warfare. Generally, mountains impede mobility, add time, and are a “sphere of danger” (265). However, the disadvantages of being in the mountains are lessened for small groups. Also, “the relative resistance in mountain warfare is,” Clausewitz asserts, “greater than in a level country” (266). The main trait of defense in the mountains is “its complete passivity” (263). For example, small posts in a good position have “extraordinary strength” (263), especially in mountainous countries.

It is possible to use the tactical results of using mountains for strategic purposes. Points to consider include using a mountainous terrain for a decisive battle or for a strategic barrier, capturing it to impact other parts of the country, or the supply of troops. For example, a mountainous district can be used for inferior combat, as a battlefield, or for general action. Minor combat may use mountains for such purposes as gaining time. Mountainous areas are typically more independent. Thus, capturing them is “much firmer” (269).

When using mountains for defense, one should be cognizant of their natural structure, ridges, and water systems for one’s own advantage. The natural mountain shape means that defense lines cannot be regular. Also, the main ridges are too dangerous for large numbers of troops. Mountain warfare comprises two key categories: defense of narrow valleys and of steep slopes. At the same time, the relative inaccessibility of mountains, allowing only small arms, make positions in the valley less dangerous. Another issue to consider is that some mountains, like the Alps, require great troop division.

Streams and rivers form strategic barriers and thus “strengthen the relative defense” (276). However, they may “either stand every blow without bending, or their defence breaks and then ends altogether” (276). In general, rivers are more useful than mountains. River defense features three key forms: “[a]n absolute defense with the main body”; a demonstration; and relative resistance (276). Defense can also be direct or indirect. For example, direct defense translates into opposing the passage and pertains to large rivers. The defending army can also effectively defend a river on the enemy’s side by cutting its communications by it. A feigned defense only intended as a “show of resistance” may also be useful in some scenarios (285).

Overall, the river’s breadth, the type of passage, and the strength of the defense are important factors. For example, when building bridges for passage one should consider the amount of time required along with the effort. Islands should be occupied because they are an obvious point of the passage. Defending a river takes time and thus provides an advantage to the defending army. The latter is contingent upon the numerical size of each side.

Important rivers serve as obstacles and thus benefit the defending troops in their own country. For example, a defending army may have a large river behind it as well as several secure crossings. Another example is when “a river crosses the theater of war more or less at a right angle with the strategic front” (287). Alternatively, the attacker may use a river for transport when its course is in a perpendicular direction to the front, because he has longer communication lines.

Swamps, marshy areas, and lowlands “form very considerable obstacles” and are thus advantageous in “an indirect defense” (287, 288). Marshes are harder to cross for infantries than rivers. However, marshes are too dangerous for the defending army to place itself on the enemy side because of the difficulty of the crossing.

Inundations are common only in the lowlands of Holland. They lie below sea level and feature other unique characteristics like their dry soil, irrigation usage, and small ditches. Cutting the dams would lead to flooding the entire country. The defending army, in turn, could use several measures, for instance, by making the dams impregnable.

“Thick” and “impassable forests” in non-mountainous terrain are another topographical feature useful for defense under certain conditions. For example, by keeping such a forest behind itself, the defending army will “conceal from the enemy all that takes place behind that army” (292). The defending army may also attempt to ensure that the enemy lines of communications pass through such a forest. However, defending forests directly is “a very hazardous piece of work” (292).

A cordon means “every defensive plan which is intended directly to cover a whole district of a country by a line of posts in connection with each other’ (292). Such a line “can only have a very small degree of defensive stamina” (292). The Great Wall of China is a historical example of such a line. More recently-made European cordon lines are meant to “check minor operations” such as raids (293). A cordon war is not meant to stop “every blow which the enemy’s forces might attempt” (294).

A key of the country is “any spot without the possession of which no one dare venture to penetrate into an enemy’s country” (295). It is a “point of commanding importance, where several roads meet” (295). In this framework, the key position is “an independent conception in strategy” only if it involves the capture of an area “which is indispensable before daring to enter the enemy’s country” (297).

A strategic flank is “a side of the theater of war” (297). Attacking from one side in battle, “or the tactical movement against a flank, must not be confounded with it” (297). Action against a strategic flank may involve two distinct objectives: to target communications and to target the line of retreat. For example, merely threatening an enemy’s line of retreat may cause him to do so. However, cutting off an enemy’s retreat entails the disadvantage of dividing one’s own forces. Such a disadvantage could be countered in a number of ways, for instance, by having a “great moral and physical superiority” (303).

A line of communication may be weak for a number of reasons, such as its direction. When targeting the line of communications, a numerically insignificant force should be used, while the enemy’s army “has run its career” (298). Clausewitz provides examples featuring different positioning of the communications line for the defenders and the assailants. One such case is when the line is long or has an oblique direction.

Overall, targeting the flank benefits the defensive side. It should take place late in the campaign. It should also occur “in a retreat into the heart of the country,” as well as “[i]n connection with a general arming of the people” (302).

A voluntary retreat deep into one’s country is “a particular form of defence through which it is expected the enemy will be destroyed” (305). Involuntary retreat after a loss in battle, in contrast, may lead to great losses as it is done in a chaotic manner and in a state of demoralization. A voluntary retreat is beneficial for the defending army in a number of ways, such as collecting provisions and finding shelter in one’s own country. In contrast, the advancing side is at a disadvantage, as was the case with Napoleon’s invasion of Russia, with Russia having a large, generally uncultivated country with “loyal and warlike people” in a difficult season like winter, which offered the best circumstances for such a retreat (307). A vast country also allows for a “sudden change of direction of a line of retreat,” which is also advantageous (311). The latter “makes it impossible for the [advancing] enemy […] to maintain his old line of communication” (311). However, the “moral impression” (307) of a retreat is also worth mentioning because a commander may face objections. Sacrificing territory in a retreat leads to feelings of “sympathy and dissatisfaction” (307).

“A people’s war” arose in Europe in the 19th century. This form of support may be beneficial for the defending army of one’s own country under certain conditions. Civilians can also support the war effort in other ways, such as voluntarily aiding with provisions or through requisitioning. The “moral element” of having “the resistance which the whole nation in arms is capable of making” is also a significant factor (314). A people’s war can be used in the heartland but “cannot be decided by a single catastrophe” (314). The country’s terrain must be difficult, and the theater of war must be expansive. The people’s army should be “a kind of nebulous vapoury essence” that never condenses “into a solid body” (315). In the latter case, it would be easily beaten by a professional army of the attacker.

Defense “is nothing but the stronger form of combat” (318). Its goals are to preserve one’s own troops, destroy the enemy, and attain victory. Victory is the goal but not “its ultimate object” (318)—that objective “is the preservation of [one’s] own political state and the subjugation of that of the enemy” (318). The latter should be attained through desirable peace terms. A “considerable weakening” of the enemy’s troops may lead to his loss of territory and ultimately the destruction of his army (318). Victory depends “on its greatness” as well as “the mass of conquered troops” (319).

The greatest effect is produced by targeting the center of gravity of the enemy. When a commander identifies this center, it is “a supreme act of strategic judgment” (320). However, there may be two opposing objectives. The first is to control the territory which divides the forces. The second is to use “force against the center of gravity,” which combines them (320). Clausewitz argues that any theater of war may be reduced to a single center of gravity.

Defense comprises two distinct features: “the decision and the state of expectation” (320). For example, an attack of another country requires “considerable preparations” for the attacker (322). This time can also be used by the defender to prepare, while keeping in mind that the latter typically takes less time. The defensive side may identify the most likely points of attack.

Clausewitz suggests that “[i]f the defender has put himself in the right position, he may be almost sure that the assailant will come to meet him” (323). He provides a number of examples of effective defense, such as attacking the enemy flank with one’s entire force or targeting the enemy’s communications. If the defending side is forced to engage in offensive actions, then his advantages include a strong position, optimal entrenchments, and others. Fortifications also help the defender in a number of ways, such as not sacrificing more territory than necessary. A retreat deep into the country should only be undertaken under certain conditions, such as gaining time.

Resistance cannot be successive in strategy and must make available all forces at once. However, when it comes to immovable elements like fortifications, they can only be brought into use gradually by the defensive side. Reinforcements can also be introduced in succession. An “extreme form” of resistance is to delay the decision by using a deep retreat into the interior (331).

The state of waiting is “one of the greatest advantages which the defensive has over the offensive” (332). However, the decision does not always arrive in real-life scenarios, but certain “tendencies of the action” remain (345). Occasionally, instead of the decision, “the focus of all action in every war [is] directed to mutual destruction” (333). In this context, the assailant usually targets capturing territory without a decisive battle, unprotected fortification, or successful combat. The defense may respond by keeping the fortifications behind it, by spreading out its troops over the given territory, and by guarding “against disadvantageous combat” (333). The defending army may also use offensive means such as targeting the enemy’s communication lines, diversions, or attacks on enemy posts.