Drums are beating for a pre-emptive war to take out such nuclear facilities as Iran might have. But considerable caution is in order, because this is basically the same story Americans heard not so long ago, in 2003, to promote the pre-emptive war against Iraq. Although the United States “won” that war, intelligence about Iraq’s alleged weapons of mass destruction turned out to be wrong, the killing has gone on for nearly a decade, Sunni and Shiite factions appear to be going at each other again, and with Saddam Hussein gone, there’s a political/​military vacuum that Iraq’s larger neighbor Iran is undoubtedly eager to exploit.

The calls for another pre-emptive war are particularly ironic considering that Iran used to be a friend of the United States. Our CIA helped the Shah secure his power in 1953, because he helped prevent Soviet penetration of the Mideast. But the Shah went on to establish a secular, authoritarian regime that made plenty of enemies. Ayatollah Khomeini became one of the Shah’s most formidable enemies as early as the 1960s. Because the U.S. backed the Shah, his enemies became our enemies, and they unexpectedly seized power in 1979. The U.S. affirmed its status as an enemy by backing Saddam Hussein after he attacked Iran the following year, in what became an eight-year blood bath.

Iranian leaders have done just about everything to convince the world that they are a bunch of dangerous fanatics, so the prospect of a nuclear Iran is scary. But by now we ought to have learned that a pre-emptive war can multiply the complications.

This is because war is the most costly, violent and unpredictable thing governments do. Again and again, even decisive victories can turn out to be serious mistakes, if not catastrophes, because of unintended consequences. While we might be able to control what we do, we cannot control how other people react to what we do.

Here are 6 reasons why wars go wrong:

1. Nations at war often try to avenge their suffering, which means they are likely to inflame hatreds that persist for a long time and provoke more wars.

In April 1917, President Woodrow Wilson led the United States into World War I. He claimed it was “the war to end wars.” He vowed that it would “make the world safe for democracy.” At that time, the war had been stalemated for three years — neither side able to impose its will on the other. By intervening on the side of the British and the French, Wilson made it possible to break the stalemate, win a decisive victory and dictate terms to the losers.

Wilson imagined he could negotiate peace on noble principles expressed in his January 1918 ”Fourteen Points” speech before a joint session of Congress. But almost a million British soldiers and civilians died in the war. Almost 1.7 million French soldiers and civilians died. Hundreds of thousands of soldiers succumbed to the influenza pandemic. In addition to battle-related destruction of property, retreating soldiers destroyed just about everything that might be useful for their adversaries. They cratered roads, burned homes, demolished factories, poisoned wells, flooded mines, ruined crops and slaughtered livestock.

Wilson, who had more formal education than any previous U.S. president, failed to understand how determined British Prime Minister David Lloyd-George and French Premier Georges Clemenceau were to avenge their grievances against Germany. Clemenceau, for instance, acknowledged that “My life hatred has been for Germany because of what she has done to France.” Wilson was hopelessly outmaneuvered during the postwar negotiations, and the result was the vindictive Versailles Treaty that had nothing to do with the Fourteen Points.

The treaty, forced on the Germans, triggered a nationalist firestorm that enabled a lunatic like Adolf Hitler to attract thousands of followers by promoting hatred and violence. If the United States had stayed out of the war, quite likely it would have ended with some kind of negotiated settlement and better long-term prospects for peace.

2. The overwhelming stresses of war can trigger economic chaos, political crises and totalitarian regimes.

As long as Woodrow Wilson was neutral during World War I, he didn’t have any reason to care what the Russians did. But when he entered the war, he had an incentive to keep Russia fighting on the Eastern Front. This tied up German soldiers there. If the Russians quit the war, as they were anxious to do, Germany would have been able to move some of their soldiers to the Western Front, causing more trouble for the British, French and Americans. So Wilson put pressure on the Russian government. His policy was “No fight, no loans.” He bribed the financially-strapped Russians.

But Russia had begun disintegrating from the day it entered the war in August 1914. Harvard historian Richard Pipes reported that “the army required each month a minimum of 100,000 to 150,000 new rifles, but Russian industry at best could provide only 27,000.” Large numbers of Russian soldiers were sent to the Eastern Front unarmed, and Russian mothers were outraged. The government conscripted some 11 million peasants into the army, which depopulated farms and caused chronic food shortages. In any case, there wasn’t enough railroad capacity both to ship soldiers to the front and ship food for the people — three-quarters of Russian railroad lines had just one track. Massive corruption undermined political support for the government. “There is no indication that the dark and violent history of Russia ever occupied Wilson’s attention,” American diplomat and historian George F. Kennan observed in Russia Leaves The War (1956), which won a Pulitzer Prize.

By keeping Russia in the war, Wilson unintentionally accelerated the disintegration of the Russian army. Kennan reported, “not only had Russia become involved in a great internal political crisis, but she had lost in the process her real ability to make war. The internal crisis was of such gravity that there was no chance for a healthy and constructive solution to it unless the war effort could be terminated at once.” Staying in the war, Kennan added, “provided grist to the mill of the agitator and the fanatic: the last people one would have wished to encourage at such a dangerous moment.” Lenin tried to seize power three times during the summer of 1917, but he failed even though hundreds of thousands of Russian soldiers were deserting. Lenin didn’t succeed until his fourth attempted coup in October 1917, when the Russian army had virtually collapsed.

On August 23, 1939, Lenin’s successor Josef Stalin approved a pact with Hitler, pledging (1) that Germany and the Soviet Union wouldn’t attack each other and (2) that they would carve up Poland. “By freeing Germany from the risk of waging war on two fronts,” noted the French historian Stéphane Courtois, “the pact led directly to the outbreak of World War II.” A week after the pack was approved, Hitler invaded Poland, and the war was underway. We might have been spared all that if Woodrow Wilson hadn’t been so anxious to have Russia continue fighting in World War I.

3. If allies have conflicting aims, a war is likely to have conflicting outcomes.

U.S. President Franklin Delano Roosevelt and British Prime Minister Winston Churchill embraced Stalin as an ally after Hitler ordered the invasion of the Soviet Union in June 1941, even though Hitler and Stalin had been odious allies up to that point. FDR and Churchill figured they needed all the help they could get.

But this marriage of convenience changed the nature of World War II. It was no longer a struggle for freedom, because Stalin ranked among history’s worst mass murderers — approximately 42 million deaths. Moreover, the Nazis developed concentration camps based on what they had learned about earlier Soviet concentration camps. Rudolf Hess, who organized Auschwitz, cited Nazi reports that “described in great detail the conditions in, and organization of, the Soviet camps, as supplied by former prisoners who had managed to escape. Great emphasis was placed on the fact that the Soviets, by their massive employment of forced labor, had destroyed whole peoples.”

Stalin exploited more opportunities to expand his Soviet empire after he allied with FDR and Churchill than before. Hundreds of millions of people were liberated from the Nazis, but most were re-enslaved by Stalin. He seized Estonia, Latvia, Lithuania, generous portions of Poland, Finland and Rumania. Moreover, Poland, Bulgaria, Czechoslovakia, East Germany, Hungary and Rumania became Soviet satellites.

On August 8, 1945, two days after the United States dropped an atomic bomb on Hiroshima, the Soviet Union declared war against Japan and grabbed more territory. The Soviet Union conquered Manchuria, Inner Mongolia, Sakhalin Island, the Kuriles and Korea. In addition, Stalin helped Mao Zedong who was fighting to establish a communist regime in China. Altogether, within five years after World War II the number of people subject to communist oppression in Europe and Asia soared from 170 million to about 800 million.

4. A vulnerable adversary can become unbeatable if it unexpectedly gains a big ally.

At the National Press Club, January 12, 1950, Secretary of State Dean Acheson gave a speech identifying nations that the United States pledged to defend from an attack. Acheson’s “defense perimeter” notably didn’t include South Korea. That nation, after all, had long been embroiled in conflicts involving its neighbors China, Russia and Japan.

Then on June 25, 1950, North Korean communist dictator Kim Il Sung attacked South Korea. North Korean soldiers crossed the 38th Parallel and entered South Korea. President Harry Truman decided to try stopping this communist aggression, even though South Korea was much less of an issue than China that had already fallen to the communists the previous year. On July 19, Truman asked Congress for $10 billion of emergency appropriations to fund a “police action” in Korea — he didn’t want to ask Congress for a declaration of war and risk having that defeated.

U.S. forces, led by General Douglas MacArthur, landed behind North Korean lines at Inchon — a very bold move — and within a few weeks he was advancing into North Korea. He did so well that Truman let him have a substantially free hand. In late 1950, MacArthur told reporters that the war was almost over.

He might have been wise to settle for occupying North Korea’s capital, Pyongyang, but he pushed his luck as he continued heading north toward the Yalu River on the Chinese border. Then came reports that indicated South Korean soldiers were “heavily engaged with a fiercely resisting [unidentified] enemy.” U.S. forces captured some prisoners who turned out to be Chinese. MacArthur began to hear that Chinese “volunteers,” as Chairman Mao called them, had crossed the border. MacArthur commented that the situation was “not alarming.” But the increasing number of shootouts suggested that a large number of Chinese soldiers might be in North Korea. Then the New York Times reported that “Chinese Communist hordes, attacking on horse and foot to the sound of bugle calls, cut up Americans and South Koreans in an Indian-style massacre.”

In fact, some 300,000 Chinese soldiers had swarmed across the border and forced MacArthur to retreat. The Chinese captured Seoul, South Korea’s capital. Eventually MacArthur battled his way back to the 38th Parallel, and the war became stalemated.. An armistice was signed on June 7, 1953. U.S. armed forces had doubled to 3 million, military spending had quadrupled, the war had cost an estimated $75 billion (real money back then), and 54,246 American lives had been lost. Six decades later, U.S. forces are still in South Korea.

5. Major powers can be thwarted by people who are fighting for their homeland, know their territory well and have nowhere else to go.

After running as a peace candidate during the 1964 election, President Lyndon Johnson authorized the escalation of the Vietnam War. He embraced the “domino theory” that a communist takeover in one country like Vietnam could result in other Asian countries falling to communists. But as noted, the biggest domino — China — had already fallen.

President Johnson seemed to view Vietnam as if it were a social welfare program. He declared, “Our foreign policy must always be an extension of our domestic policy” — namely, his Great Society entitlements. “I want to leave the footprints of America [in Vietnam]. I want them to say, ‘This is what Americans left — schools and hospitals and dams.’” Johnson’s Vice President Hubert Humphrey was even more carried away by the dream of doing good in Vietnamese jungles: “We ought to be excited about this challenge, because here’s where we can put to work some of the ideas about… nation-building… new concepts of education, development of local government, the improvement of health standards… and really the achievement and fulfillment of full social justice.”

Johnson made many mistakes besides having unrealistic expectations. He micro-managed the war and severely restricted what military commanders could do. His policy of gradual escalation seemed to convince the communist North Vietnamese that the United States was a reluctant warrior who could be defeated if they persisted long enough. Johnson and his top brass over-estimated the American advantages of superior weapons, especially air power.

Such policies led many observers to believe that if only the military had been unleashed, they could have won the Vietnam War, but there are reasons to doubt that. Vietnamese were fighting on their homeland. They knew the jungles well, they had nowhere else to go, and their survival was at stake. Americans didn’t know the jungles, everyone figured that eventually we would go home, and American survival wasn’t at stake, because the United States was more than 8,000 miles away. Moreover, since North Vietnamese insurgents wore ordinary civilian clothing, and they mingled among the South Vietnamese, American soldiers could never be sure which were the people they were trying to help and which were the enemies plotting for murder and mayhem. These are crucial advantages that native people always have when dealing with a foreign military presence. Such advantages go far to explain why major powers have become bogged down in guerrilla wars.

6. People don’t want somebody else building their nation, even when they’re making a mess of it — especially during a civil war.

In 1957, the U.S. Central Intelligence Agency fixed parliamentary elections in Lebanon. Former CIA officer Victor Marchetti recalled, “the CIA had helped elect so many pro-American candidates that the established Arab nationalist politicians were furious, realizing that the cheating was eroding their power base. The feud that had been brewing between Arab nationalists and the pro-Western Christians erupted into civil war. President Eisenhower sent in the marines. They were withdrawn after a few months, but what had been perhaps the most stable state in the Middle East was on the road to total polarization and eventual disintegration.”

A quarter-century later, U.S. and French forces were in Lebanon again. They attempted to serve as peacekeepers amidst the civil war that raged on. In October 1983, two truck bombs struck the barracks — an inviting stationary target. Among the dead were 58 French personnel and 241 Americans. The American death toll included three Army soldiers, 18 Navy seamen and 220 Marines. Apparently recognizing the futility of trying to referee a civil war, President Ronald Reagan ordered that U.S. forces be withdrawn from Lebanon.

In 1993, Bill Clinton imagined that the U.S. could build a nation in Somalia — or as Clinton’s then-UN ambassador Madeleine Albright put it: “nothing less than the restoration of an entire country.” The first step was to be the disarming of warlords. Of course, they wouldn’t be warlords without their guns, so the U.S. found itself embroiled in another civil war. Tragically, American soldiers were killed for nothing that involved a vital U.S. interest, certainly nothing that well-intended intervention was capable of resolving. Clinton recognized the futility of the intervention and withdrew U.S. forces.

The following year, however, Clinton was at it again. He ordered 20,000 U.S. soldiers to Haiti, so they could help alleviate hunger and establish a democracy. Eight years later, Haitian poverty rates were higher, literacy rates were lower than when the mission had begun, and political turmoil persisted. Why was anybody surprised at the futility of this intervention?. Since Haiti gained independence in 1804, Historians Robert Debs Heinl, Jr. and Nancy Gordon Heinl described it as “a country with nearly 200 revolutions, coups, insurrections and civil wars.”

After 9/11, President George W. Bush ordered U.S. forces into Afghanistan to destroy the camps where al-Qaeda terrorists were trained. This mission became a decade-long (and counting) nation-building project. Now, although almost 2,000 U.S. soldiers have died there and hundreds of billions of dollars have been spent fighting, Afghans continue to grow opium, stone women and engage in bloody power struggles. One might have thought that our sacrifices would have at least bought a loyal ally. But Afghan President Hamid Karzai declared his country would side with Pakistan in the event of a conflict with the United States. The British weren’t able to reform Afghanistan, nor could the Russians, and it’s doubtful whether we’ll be able to do any better.

Clearly, if government intervention cannot save relatively small nations like Lebanon, Somalia, Haiti or Afghanistan, there’s no reason to believe the world can be saved by having our government spend more money and order more American soldiers into harm’s way. Washington would do well if it could save itself from bankruptcy as a result of runaway spending and debt.

What people everywhere need is more freedom and free markets. We can’t force these things on others, but we can reverse anti-business policies that have throttled the American economy. When America becomes a dynamo again, more people overseas will find it in their self-interest to adopt the kinds of policies that work for us, much as millions of people embraced English as a principal language of business, science, technology and popular culture.

We need less foreign intervention, not more, to avoid gratuitously making enemies and contributing to difficult situations like we face with Iran now. This means restraining the government sector — the sector of bellicose rhetoric, seizures, embargoes, blockades, sanctions and wars. We need to encourage more voluntary, people-to-people international relations by businesses and nonprofits as well as individuals. Government can help do this by reducing restrictions on the movement of people, goods and capital.

Meanwhile, we need to be vigilant about maintaining a strong national defense that can protect us against aggression and perhaps more important, a strong national defense that can convincingly deter aggression. Deterrence is probably our best bet with Iran as it proved to be with the Soviet Union and China. Britain’s Prime Minister Margaret Thatcher paid Ronald Reagan a supreme compliment when she declared that “He won the cold war without firing a shot.”