Preventive wars and preemptive strikes are both risky business. A preventive war is a military, diplomatic, and strategic endeavor, aimed at an enemy whom one expects to grow so strong that delay would cause defeat. A preemptive strike is a military operation or series of operations to preempt an enemy’s ability to attack you. In both cases, a government judges a diplomatic solution impossible. But judgment calls are debatable and preventive wars often stir up controversy. Preemptive strikes run the risk of arousing a sleeping enemy who, now wounded, will fight harder. Yet both preventive wars and preemptive strikes can succeed, under certain limited circumstances. Consider some examples.
The Peloponnesian War (431-404 B.C.) is the granddaddy of all preventive wars. The Peloponnesians, led by Sparta, decided to make war on Athens less because of a series of disputes dividing the two blocs than because of the future that they feared, one in which Athens’ growing power would break apart Sparta’s alliance system. The Athenians wanted to decide the two sides’ dispute via arbitration, but the Spartans refused, which cost Sparta the moral high ground. Before Athens and Sparta could fight a proper battle, the war began. Sparta’s ally, Thebes, launched a preemptive strike on the nearby city and Athenian ally, Plataea.
Both the preemptive strike and the preventive war succeeded but at no small cost. It took four years of hard fighting and considerable escalation before Plataea surrendered. Sparta emerged victorious against Athens but only after 27 years of intermittent and escalatory warfare. The price of victory was steep, leading to embroilment in war against Persia, a falling-out with Sparta’s former allies, and ultimately, the collapse of the Spartan regime after centuries of stability. Athens lost the Peloponnesian War, but managed to preserve and even strengthen its regime at home; it never successfully restored its overseas power.
To turn to another ancient case, Rome frequently engaged in preventive war. The most egregious example was the Third Punic War (149-146 B.C.), when Rome declared war on Carthage. Carthage offered no serious threat for the foreseeable future, if ever, because Rome had thoroughly defeated it twice in the past. Yet some Romans feared the growing prosperity of its long-time rival. The war was hard-fought but led to a complete Roman victory. After a lengthy siege, Carthage was destroyed. It ceased to exist as a polity. For a century it wasn’t even a city, but then it was re-founded—as a Roman city.
Turning to modern times, Japan fought a preventive war against Russia in 1904-1905 in order to stop the Russians from building up their strength in the Far East, particularly via a railroad through Russian-occupied Manchuria. The Japanese launched the war with a preemptive strike, a surprise attack on the Russian naval base at Port Arthur. The strike weakened the Russian fleet but did not destroy it. Ultimately Japan was successful at sea but compelled to accept a stalemate on land. The outbreak of revolution in Russia forced the Russians to the peace table and handed Japan victory, but although Japan bruised Russia badly it did not win the war on the battlefield.
In June 1967 Israel launched a series of preemptive strikes against Egyptian and other Arab air forces. A devastating success, it contributed greatly to Israel’s victory in the Six Day War. In 1973 Egypt and Syria launched a series of highly successful surprise attacks if not preemptive strikes. Although Israel bounced back by dint of effort and with American resupplying, the Arab states’ military successes, along with their use of the Arab “oil weapon,” led to victory, especially for Egypt.
None of the belligerents in 1973 had to convince their people to fight, but not all politicians have that luxury. In Rome before the Third Punic War, for instance, the leading war hawk, Cato the Elder, frequently ended his speeches in the Senate with the statement that Carthage must be destroyed. It took an effort to convince the senators to fight a preventive war against a less-than-obvious threat, but it is even more difficult to convince modern liberal democratic societies to do so. Popular and successful politician though he was, U.S. President Franklin D. Roosevelt did not dare ask Congress for a declaration of war against Nazi Germany or Imperial Japan until the Japanese attack on Pearl Harbor on December 7, 1941. Yet both regimes were expansionist powers offering widely—but not unanimously—acknowledged threats to American security. Even after Pearl Harbor, Roosevelt asked Congress for a declaration of war only against Japan, even though the U.S. and Germany were engaged in an undeclared shooting war in the Atlantic. Not until Germany declared war on the U.S. on December 11, 1941, four days after Pearl Harbor, did the U.S. Congress declare war on Germany.
Most would consider the Japanese attack on the U.S. in 1941 a preventive war by Japan, before the U.S. could intervene in the Far East. The Japanese might say that American economic strictures such as freezing Japanese assets and embargoing oil were tantamount to acts of war. In any case, Japan launched a preemptive attack on both the U.S. navy and air force in Hawaii on December 7, 1941. The strike did great damage but left the Americans with more than enough resources to rebound and win the war. This despite Japan’s ability to inflict a second damaging preemptive attack on the U.S. air force in the Philippines, a little over nine hours after news of the Pearl Harbor attack had arrived.
The U.S. fought a preventive war in Iraq in 2003 against the threat of Saddam Hussein’s program of weapons of mass destruction. Some in the U.S. government also hoped to turn Iraq into an ally. The invasion succeeded in defeating Iraqi conventional forces, occupying the country, and toppling Saddam. Yet U.S. intelligence concluded that although Saddam’s goal was to recreate his WMD program, that program had been destroyed in 1991. Public support for the war in the U.S. wavered after the emergence of an Iraqi insurgency. In spite of eventual success by a U.S. counter-insurgency campaign, a change of government in the U.S. brought a complete withdrawal of remaining American troops from Iraq. Today Iraq has no WMD but it is a divided state, reeling from war with ISIS, and in large part an ally of Iran rather than the U.S. If preventive war was a success, it came at a heavy price.
To sum up, preventive wars and preemptive strikes work only under certain conditions. If the attacker carries out a brilliant operation, has overwhelming military superiority, is able to mobilize political support particularly at home but also abroad, and is willing to pay a heavy price and bear a long burden in case the war drags on, then one of those two moves might make sense. States lacking those strengths would do best to avoid such risky endeavors.