Thucydides and the Long War Problem


Editor’s Note: This is the fifth installment of “The Brush Pass,” a new column by Joshua Rovner (@joshrovner1) on intelligence, strategy, and statecraft.

Is there anything left to say about Thucydides?

In a year dominated by concerns over modern technologies — ballistic missiles, nuclear warheads, and cyber weapons — scholars have spent a remarkable amount of time arguing about a very old conflict. Thucydides’ classic history of the Peloponnesian War documents the catastrophic fight between Athens and Sparta from 431–404 BC. It was a horrendous affair. Conventional combat, gruesome disease, mass murder, and civil war tore apart the fabric of the ancient Greek world. The post-war was chaotic, violent, and impoverished.

Thucydides’ account of the war itself describes several enduring strategic dilemmas: when and how to take risks, how to balance the demands of domestic politics against the requirements of strategy, how to deal with audacious military commanders, and so on. But of all the issues contained within the book, perhaps none is as important as the explanation for why great powers become trapped in prolonged conflicts they thought would end quickly. Thucydides shows us that in the fevered run-up to war, leaders delude themselves that they can win without beating the enemy on its turf. Sea powers seek victory over land powers without destroying their armies, and vice versa. Early battles settle nothing because both sides can safely retreat to their respective domains. The result is stalemate: Neither side has the military wherewithal to force surrender, and neither will back down because the political stakes are so high.

In the years before the war began, both sides were aware of their comparative strengths and weaknesses. Athens, the dominant sea power in ancient Greece, had implemented a grand strategy combining trade and imperialism. Its security rested on its navy, its system of tributary allies and colonies, and the long walls that encircled the city and connected it with the port at Piraeus. Spartan security, on the other hand, rested on its powerful infantry, which it used to dominate most of the Peloponnese. Unlike Athens, it thrived because its grand strategy was inherently conservative. Sparta’s famous phalanx was lethal, but Spartan leaders were loath to send it abroad, because doing so might encourage its serfs to rise up in rebellion.

The situation resembled what some today call “cross-domain deterrence.” Contemporary strategists wonder if it is possible to deter military action in one domain with threats in another. For example, can the United States deter cyber-attacks by demonstrating its capability and willingness to respond with conventional military force? Will U.S. naval dominance continue to offset China’s land power, preventing the two nations from stumbling into war as Graham Allison warns? More generally, is it possible to construct a stable balance so that technological breakthroughs in one area do not encourage states to take extraordinary risks?

Something like cross-domain deterrence kept the peace in ancient Greece for a time in the middle of the fifth century BC. Athens dominated the water but had obvious reasons to avoid pitched battle with the Spartan army. Sparta had the most powerful land forces in Greece but had little hope against skilled Athenian oarsmen.

Both sides were aware of this basic asymmetry, but in the frenzied pre-war period, they indulged in fantasies about winning without having to face the enemy’s center of gravity. Athens hoped that small-scale raids on the Peloponnesian coast would inspire a revolt among the Helots — Sparta’s state-owned serfs. Sparta hoped it could convince Persia to join the war — and bring its formidable navy. None of these hopes panned out, and, predictably enough, the war settled into a frustrating deadlock after a series of inconclusive battles in the first few years of fighting.

Unable to overcome their opponents’ key strengths, but protected by their own domination of their respective domains, Athens and Sparta fell into familiar approaches to war. Neither was willing to attack the enemy where it was strongest, meaning both were safe from conquest but also unable to compel the other to do their will. The result was a costly stalemate lasting decades.

Tactical caution ruled the day. Commanders from both sides retreated upon hearing that enemy forces were nearby. Sparta broke off promising amphibious operations in 429 and 428, and abandoned its allies in Corcyra’s civil war at the moment it seemed possible to break away one of Athens’s most important allies. Athenian land commanders followed the same pattern, avoiding engagements in 425 and 424 after receiving intelligence that the Spartans were coming. Athens also failed to fully support Argos in its battle with Sparta in 418. This battle — the largest of the whole war — was a near-run thing, and a crushing land defeat on the Peloponnese might have proven disastrous for Sparta. But Athenian leaders, chastened by memories of earlier disappointments, committed only a small force to the battle.

Bold commanders were hard to find, and the exceptions, like Brasidas of Sparta, had to willfully ignore orders in order to pursue audacious campaigns. In other cases, political leaders sought to rid themselves of risk-acceptant leaders by sending them on campaigns that they thought were unlikely to succeed. Athenian leaders famously sought to get rid of Cleon by sending him on what they though was a fool’s campaign against Spartan forces on the southern coast of the Peloponnese. (To their amazement, he won.)

Risk-averse commanders led military forces that were doctrinally limited to indirect efforts to attack the enemy. The fact that both sides enjoyed geographic sanctuaries — Sparta on land, Athens at sea — meant that neither was forced to give up. And because both sides thought they were fighting for existential political stakes, neither was enthusiastic about giving up.

But fighting to avoid losing was costly. Indeed, 27 years of inconclusive campaigning was exhausting to both sides. Sparta finally defeated Athens in 404, tore down its walls, and occupied the city. Its victory was temporary and hollow. The costs of fighting for so long had left it open to predation from other rising great powers, and it went into a century of decline. Still facing the threat of Helot rebellion, it suffered a devastating defeat to Thebes in 371 BC, and was subsequently unable to prevent the rise of Macedonian hegemony. Sparta’s time as the dominant land power in Greece was over.

When Americans today think of protracted wars, they think of the painful counter-insurgencies against non-state armed groups in Vietnam, Afghanistan, and Iraq. Conventional wars against regular military forces, by contrast, have been astonishingly short, with historically low casualty ratios. But the chance of a prolonged conventional war has not disappeared, despite enduring U.S. advantages in technology, resources, and military professionalism. A conflict against China, for instance, could follow the Peloponnesian pattern. As I describe in the Journal of Strategic Studies, strategists in both countries hope for rapid victories at low costs, with cyberattacks and other information operations crippling the other side’s ability to coordinate an effective defense.

The initial stages of a conflict may not work out as planned. Indeed, opening campaigns in great power wars rarely follow expectations. As the naval historian John Maurer recently put it, “In wars involving great powers, the first round of fighting is not likely to prove the last.” Miscues and mistakes are likely in complex campaigns requiring coordinating multiple services over vast stretches of sea and air. In the event of a disappointing start to a war in Asia, U.S. forces could retreat to the sea, trusting that their regional allies have sufficient defensive capabilities to keep Chinese forces at bay. Meanwhile, China could find refuge on land, settling into a war of harassment against U.S. and allied forces. Neither side could easily compel the other to accept defeat, but neither would face the immediate danger of destruction.

In such a case, adroit diplomacy would be needed to convince leaders to stand down. Both sides will view the outcome as crucial, even existential, or they would not have taken the risk of war against a nuclear-armed great power in the first place. U.S. leaders may view the war as a final test of the post-war liberal order that they spent so much blood and treasure building. The Chinese Communist Party will feel intense pressure to avoid capitulation, especially if the war involves deeply nationalist issues like the status of Taiwan. Choreographing a settlement acceptable to the United States that also allows Chinese leadership to save face — and even claim victory — will tax even the most brilliant strategist.

Such a settlement proved impossible in ancient Greece. Modern strategists would do well to ask why.


Joshua Rovner is Associate Professor in the School of International Service at American University. He is the author of Fixing the Facts: National Security and the Politics of Intelligence (Cornell, 2011), and writes widely about intelligence and strategy.