On Defense and Offense: Revisiting Clausewitz, Mao Zedong and Thucydides

“No bastard ever won a war by dying for his country. He won it by making the other poor dumb bastard die for his country.” Patton’s remark, while it had not advanced the study of war by any measure, stated what had been the objectives of military commanders of history: to defeat the enemy and preserve their own forces. Clausewitz, in order to elaborate the importance of attack and defense to the theory of war, said it longer and more philosophically: “as I have not overthrown my opponent I am bound to fear he may overthrow me” [and one third of his first chapter of the first book of On War].[1]

This article delves into the theory of the dynamic relationship between offense and defense. It aims to answer the question: how commanders and leaders in history have made their decisions to defend or attack and switch between the two postures on a strategic level. What reasons have influenced their doing so? In order to do so, the author will track the development of the theories of defense and offense from the age of Clausewitz to the mid-20th century guerrilla warfare theorist Mao Zedong. These theories will then be applied in a case study from the Peloponnesian War to further deduce the relationship between offense and defense. The article will provide readers with not a prescriptive guide of how commanders should switch between offense and defense, but a descriptive analysis of how commanders would do so.

The basis of defense and offense theory: Clausewitz versus Jomini

Clausewitz argues that the decision to attack or defend depends on the unique circumstances a commander faces. As early as 1808, when he saw Jomini’s critique of Frederick the Great for not being aggressive enough, he came to defend the king. Clausewitz objected that Jomini had not accounted for the political, social, and technological differences between earlier centuries and the Napoleonic era, or the differences in the commanders’ personalities. If Frederick had remained on the defensive in the latter half of the war, it was not only because of Prussia’s limited strength but also because Frederick was reacting to his experiences in earlier campaigns. Jomini’s evaluation of Frederick and Napoleon was flawed because it passed over their respective situations and ignored the manner in which two different individuals responded to their differing experiences.[2]

Another notable is Clausewitz’s attention to defense. In his model, the paradox between defense and offense constituted the interaction that made up one of three extremes that defined war.[3] He tried to explain several seemingly contradictory observations he made during his career: defense is a stronger form of war than offense,[4] yet Napoleon’s aggressive way of war was superior to the old 18th-century methods. In his earlier attempts, he tried to define defense as consisting of a stage of waiting[5] but then admitted that an attack could also involve a stage of waiting.[6] At that time, the first proposition could be explained rather successfully. Defense itself offers no reward, so why would someone adopt this posture if it were not a stronger form of war?[7] However, his other arguments fell apart: the superiority of defense is tied to external factors such as time, geography, and numerical superiority.[8] Or, the habit of halting an attack through siege, maneuver, and fortification is bad because defense in this case is “spoiled by the virus of the attack!”[9]

Later, after Clausewitz discovered the political purpose of war, he developed a sound theoretical model of defense and offense. By then, he defined an attack as an act of war with a positive aim and defense as an act of war with a negative aim.[10] Now all propositions can be explained as such. Defense is a stronger form of war because its negative aim, which is pure self-preservation, demands less effort to succeed.[11] Napoleon and his system could pursue war with more political will than his opponents, hence his superiority. Defense is a negative action, hence cannot increase the chance of success in an aggressive war, a war with a positive aim; yet the counter-offensive can do the inverse: achieve victory in a defensive war.

Thus, in Clausewitz’s view, an act of defense or offense is not only affected by the commander’s psyche but also by the political objective of the operation. Always permeating throughout the war, it was the political objective that defined an operation’s aggressiveness at its conception[12]. The question of a leader’s decision to attack or to defend can be understood as whether he is pursuing a positive or negative course of action. Whether he is seeking a reward or conserving the status quo?

Another factor that makes the commanders switch their stance is the concept Clausewitz called the culminating point of attack/victory (CPA/CPV), which are usually associated with operational and strategic levels respectively [13]. On the strategic level, the effects of CPV can be described with these scenarios:

• If he conducts an aggressive war aimed at disarming the enemy, the CPV does not appear. While his offensive power decreases as usual, he has no choice but to expend it, because his advantage gained by victory is but a means to an end [14]. Modern scholars may have different views, as Bassford argues that ambitious political leaders can cross the CPV when trying to overthrow the balance of power and get others united against them [15].
• If he conducts an aggressive war but does not aim to disarm the enemy, a timid one may end the campaign prematurely while an enterprising one may overshoot it. His enemy may capitulate early, or he has to push his last strength to achieve it [16]. Of course, it is in his best interest to stop right at CPV and switch to defense, but it’s also in the enemy’s interest to prevent him from doing so [17]. The commander may decide to launch a preemptive attack or wait to deflect his enemy’s blow.
• In a defensive war, objectives identified by Clausewitz range from launching a temporary invasion, increasing the enemy suffering, to wearing down the enemy [18]. The causes of the invading army’s loss of strength [19] do not apply to those objectives. Therefore, there is no CPV mentioned in this case.

Summarily, while the CPV may act as a signal for commanders to change their posture from offensive to defensive, the final decision also depends on the war objective and the commander’s psyche. Clausewitz did not provide a recipe to identify this point but delegated it to the commander’s genius. To him, it was actually more usual for a commander to miss it than to hit the mark. It is even more complicated to know if another commander can correctly apply it, and his action in one war does not guarantee that he will hit the CPV in others. It can be mitigated by studying each side’s objectives and the commanders’ patterns of action in war.

From definition to model: from Clausewitz to Mao

While Clausewitz divides one side’s war into two phases: a defense phase followed by an attack phase, Mao divides the war into three phases: a pure defense phase, possibly

a strategic retreat or pure self-preservation phase, followed by an equilibrium phase with back-and-forth attacks in which neither side claims superiority over the other, before finally turning into a strategic offensive.[20] It is worth noting the context here: Clausewitz mainly experienced the seasonal campaigns of his time, while Mao’s writings served as guidance for his long war against the Nationalists and the Japanese.

Both theorists shared a similar view about the role of the balance of power in dictating the course of war. Clausewitz explicitly stated that when the balance of power tips in favor of one side of the war, that side goes to the attack phase, and vice versa.[21] Mao implicitly acknowledged the same thing: the evaluation of the balance of power pushed one commander from organizing a local offensive into a strategic, all-theaters offensive.[22] A revolutionist commander, in pursuit of victory, would need to push the balance of power into the phase in which he or she is dominant over his or her enemies. Here we make the connection with Clausewitz’s definition of attack and defense: an action aimed at tipping the balance of power in our favor is an action with a positive aim. Thus, in Mao’s model, it is the attack alone that causes the transition between phases of war: if it fails, it tips the balance in favor of the defending side; if it succeeds, it augments the superiority of the attacking side.

In detail, while the revolution’s objective is offensive in nature [23], it did not exclude the Chinese Communists from initiating the Long March. This strategic retreat, in Mao’s view, was part of the strategic defensive phase[24], before being followed by a counter offensive[25] or positional defense[26]. The process in which this retreat phase ends shares the same mechanics as how Clausewitz’s defense phase ends: as the attacker (in Mao’s context, Imperial Japan) advances deep into the territory, his strength decreases and eventually he needs to stop to consolidate his gain[27]. On the other hand, to transition from the second phase to the last, strategic offensive phase, commanders will need to actively improve their position: raise their own quality and quantity of troops[28], organize regional offensive, before a nationwide offensive can happen.[29]

From these, we have our first observation:

In war, it’s the current balance of power and the desired balance of power (military aim) that dictate the commander’s decision to go on the attack or the defense.

Similarly, they agree on how the role of the commander’s personality would affect his decision to switch phases in war. Clausewitz actually paid more attention to the transition from attack to defense: he warned that a cautious commander might stop the attack too soon before it bears fruit; while an overconfident commander might overshoot the culminating point of the attack.[30] Mao, on the other hand, paid more attention to the “terminal point of retreat”, the transition point from pure defense into partial offense.[31] A too conservative commander, who exhibits “retreatism” psyche, might overestimate the enemy’s superiority and stay in retreat and defense for too long; while a too confident commander, who is “leftist opportunistic” would go on the offense prematurely.[32]

Fig 1. Representation of Mao’s three-phased war model. War then can be seen as a pushing contest with each side trying to push the other to the capitulation point. At each terminal point, the cautious commander underestimates the balance of power, while the overconfident commander overestimates it.

Our second observation:

A commander evaluates the balance of power and military aim subjectively and thus, makes the decision to switch phase in war subjectively.

Case study: the Peloponnesian War by Thucydides

In the final section, Mao’s model which has been covered in the above section will be applied to investigate several situations in the 2nd Peloponnesian War. Spanning over 20 years, this long conflict contained multiple phases during which the balance of power shifted several times. The Napoleonic Wars and The Chinese Civil War had been characterized by extreme political and military objectives, and thus, both theorists had treated the objective as constant. The Peloponnesian War, meanwhile, had seen both Athenian and Lacedaemonian[33] military objectives fluctuate, caused by differing political objectives, over the range from rendering the opponent defenseless to a pure defense or keeping the status quo. We can now track how these fluctuating objectives, coupled with the shifting balance of power, affect the strategy of both sides’ commanders.

The initial balance at the beginning of the war

In 435 BC, the conflict between Corinth and Corcyra escalated and dragged the two hegemonic alliances, one led by Athens and the other by Sparta, into direct conflict. For Athens, the reason they sided with Corcyra was the fear that the third largest navy in the Hellenic world would fall into Sparta’s hands.[34] For Sparta, it was because Corinth, and later Megara, Potidaea, the cities which had been harmed by Athens’ policies, were key members of their hegemony alliance.[35]

Initially, the Athenians followed Pericles’s defensive strategy to avoid battle with Sparta’s hoplites, evacuate their citizens and belongings into their walled city, and perform naval raids against the Peloponnesian coast.[36] Sparta, compelled by Thebes’ attack on Plataea, made inland raids into the Attic countryside.[37]

Both Sparta and Athens were dragged into this war, not primarily for their own interests, but for the interests of their allies. Yet why had they chosen different courses of action, with one side staying on the defensive and the other on the offensive?

The differing strategies were caused by differences in security situations. In a modern view, Sparta, while a land power, was actually surrounded by her helot subjects who readied to rebel against them,[38] several powerful allies such as Corinth and Thebes who were ready to ignore Sparta’s wishes or join hands with her enemy,[39] resurgent old rivals like Argos and new rivals like Elis.[40] Athens, a sea power, was protected by the Long Walls and supplied through her overseas empire. While she was not invulnerable, since her grain supply route from the Black Sea could still be cut,[41] and the Persians or her own allies might seek to dismantle her empire, these weaknesses could not be seriously targeted unless by an equal naval power.

The ancient views of Archidamus and Pericles are mostly similar: Athens was superior in resources, financial readiness, ships, sailors and naval experience; Sparta could only hope to match this with help from barbarians and religious money. The Peloponnesian army was superior and could ravage Athens’ land, but Athens could survive through imports. Archidamus had feared most that Sparta’s reputation could be ruined by inactivity and thus had to launch an attack.[42] Meanwhile, Pericles was satisfied with the current balance of power. His only fear was that Athenians might attempt overly ambitious and risky expeditions due to frustration as the war dragged on.[43]

Our third observation:

When belligerents in war are in an equal balance of power: if one side aims for an equal balance of power, it has a tendency to stay on the defensive and preserve what it has gained. If it aims for a more advantageous balance of power, it has a tendency to go on the offensive to achieve its aim.

The plague’s effect

Pericles’ vision was not common among Athenian politicians. Many war hawks, led by Cleon, demanded a more aggressive stance against Sparta. In hindsight, we know that Cleon’s faction demanded the restoration of the border during the height of the First Peloponnesian War, with strategic territory acting as buffers against Sparta’s hostility.[44] That pitted him against Pericles and his policy of preserving the status quo. The developments during 431-429 BC would strengthen the war faction’s position in Athens’ internal politics. Having already suffered the second ravaging of Attica, the draining of her treasury caused by the continuing siege of Potidaea, the catastrophic plague of 430/429 BC,[45] Spartan rejection of Athens’ peace offer in 429 BC[46] would seriously discredit the peace faction’s standing and strengthen Athens’ resolution. Even Pericles, reflecting upon the new situation, began to include a more imperialistic tone in his speech.[47]

After deflecting Lacedaemon’s new effort in naval warfare,[48] Athens would go on the offensive in 426 BC. Having already suppressed the revolt in Lesbos and the coup at Corcyra, Athens sent raids against Melos and Boeotia — the first time they went on the offensive against Lacedaemon’s allies. By 425 BC, the Athenian generals already had designs for action in Sicily, Corcyra or Peloponnesian coast. However, it was Demosthenes’ plan at Pylos that would eventually lead to victory at Sphacteria and change the course of the war.[49] Here, we can conclude that under internal pressure, Athens shifted from a defensive strategy to a counter-offensive.

For Sparta, a similar response occurred after their defeat at Sphacteria and again, when Argos’s force captured Orchomenus in 419 BC and threatened to cut off Sparta from her northern allies. Each time, faced with a crisis, Sparta would find the political will to test out unorthodox methods. In the first case, she finally approved Brasidas’s expedition into Thrace[50] and in the second time, her entire army would march against the Argives, leaving Sparta undefended.[51]

The Sicilian Expedition

In 416/415 BC, two Sicilian poleis, Segesta and Leontini, successfully persuaded Athens to intervene in the situation in Sicily. While their arguments at first resembled those of Corcyra at the start of the war: if Athens left Syracuse’s power unchecked, that city would conquer entire Sicily and channel the island’s resources to Sparta’s aid, we need not believe Athens had the same defensive aims as when they came to aid Corcyra. At that time, two dominant Athenian politicians had different visions about what Athens should do next: Alcibiades wanted to support Argos’s coalition and go directly against Sparta, while Nicias wanted to recover Thrace and Chalcidice.[52] The act of intervention in Sicily itself and the plan employed to do it clearly showed a great surge in confidence among the Athenians, which had never been seen during the war. At first, only a small force would be sent to Sicily; Athens’ effort would rely entirely upon their local allies. Later, the force grew to a gigantic size with 134 ships and 5000 hoplites, not counting later reinforcements.[53]

Our fourth observation is thus:

When the balance of power has tipped in favor of one side:

The weaker side’s reaction:

• • If their aim is limited only to survive as an independent force, the situation does not press them to change strategy.
  • If their aim is to achieve at least an equilibrium in the balance of power and they judge that the disparity of power is not so great that they still have the ability to conduct offensive, they have greater pressure to conduct offensives to restore the balance of power.
  • If the disparity of power is so great that their survival is threatened (like the first case), they have to stay on the defensive.

The stronger side’s reaction:

• • If they have not gained the desired balance of power (their military aim), they will continue to attack to achieve it.
  • If they have gained the desired balance of power, they will have less pressure to push on attack. However, as their opponent’s power grows weaker and their power grows stronger, they have less pressure to stay on the defensive to preserve what they gained. They might conduct offensives if they wish to quicken the end of the war, or to achieve additional gains.

Analysis

Except for the brief period from 405 to 404 BC, when Athens was clearly defeated and put under siege, the war saw both sides having roughly equal shares of ups and downs. The observations from the war validate Clausewitz’s theory: Athens’ initial defense strategy aligns with his description of an awaiting enemy’s offensive strategy, and Athens’ and Lacedaemons’ strong reaction against losses proves his notion that the defending side stiffens his commitment when in real danger. The progress of the war also matches the description of the second phase of Mao’s model, in which both sides conduct alternating local offensives.

Demosthenes’s action in the capture of Pylos

In the campaign season of 425 BC, an Athenian fleet set sail, with three objectives in mind: to provide aid to Athens’s forces in Sicily, to provide aid to allies in Corcyra, and to raid the Peloponnesian coast[54]. The two former objectives were continuations of Athens’s previous activities in Sicily and Corcyra, but the last was entirely Demosthenes’s idea. As mentioned above, it was his idea that led to the victory at Sphacteria. However, it required a string of lucky coincidences for the battle to happen[55]. At the beginning, he simply thought of Pylos as an advantageous position from which Athens’s force could make incursions into Spartan territory[56]. His fellow commanders objected to this plan twice, even when they were already stranded at Pylos by chance. The urgent need to reinforce Corcyra played a role, but mainly the idea was dismissed as reckless and a waste of “state expense”[57]. This case is distinct from the above examples in that it did not stem from the differences in political objectives. There was no debate about whether Athens should preserve the status quo or knock out Sparta for good. Demosthenes, who last year had broken from Athens’s strategy to attempt a flanking movement into Boeotia[58] (and suffered a heavy defeat), had toned down his ambition and become aligned with current strategy. Rather, it was an example of how the commander’s psyche was at play in his switch to the offensive. His deviating from Periclean strategy was only an escalation from previous actions: instead of temporary landings on enemies’ territory, it was a permanent fortified place[59]. Always a bold and daring commander, Demosthenes’s eagerness to mount a counterattack against Sparta was earlier than that of his fellows. As it would unfold during the Pylos campaign, the situation would eventually make the other Athenian commanders relent and follow Demosthenes’s lead, to the conclusion at Sphacteria.

From the Spartan side, this phenomenon was clearer. After the Athenian Sicily disaster, except for several lulls after suffering great naval defeats, Sparta’s objective was unchanged: to dismantle the Athenian empire and make her unable to perform hostile acts against Sparta and her allies[60]. For this end, multiple officers were sent to Asia Minor. The difference in their performance could not be explained by the difference in their objectives, but only by the difference in their character[61]. However, those officers mostly operate on the operational level because the strategy had been decided in Sparta. Thus, Demosthenes is our closest example of a commander in Mao’s theory, who, while following an objective that had been set out, initiated a shift in the phase of war through actions influenced by his character.

Conclusion

The article began with the question: what factors compelled historical commanders to decide whether to attack or defend and switch between them on a strategic level? Throughout its sections, the article first examined Clausewitz’s views on attack and defense to establish the two fundamental factors that Clausewitz identified as the answer to that question: commander’s psyche and the balance of power (more specifically, the difference between current balance of power and the desired balance of power). Mao’s theory, in essence, agrees with Clausewitz’s two mentioned factors but expands upon them and provides a different model. As two theorists’ writings had focused on total war, a kind of war with extreme political and military objectives, the article studied the Peloponnesian War to see how Mao’s model would apply to a war with limited objectives.

In studying the Peloponnesian War, several examples were examined for the role of political objectives in affecting commanders’ decisions in choosing offensive or defensive postures. One last example was reserved for studying the role of the commanders’ psyche in their decisions to switch to the offensive. As this article concludes, the author hoped that it would provide useful arguments for the discussion of the topic.