It’s a view that, despite being as ancient as Homer’s account of the Trojan War, has only recently gained traction and then only in some parts of the world. Interstate wars have been in decline, and the European continent that was once so often torn apart by war has become remarkably peaceful. Even among dictatorial regimes and in poorer countries, a nation’s government waging war against its neighbors has become a rarity, though certainly not unknown.

So why has the United States not joined in this aversion to interstate war? Since 1945, America has engaged in wars in Korea, Vietnam, Panama, Somalia, Afghanistan, Iraq, and Libya and smaller interventions in a plethora of other nations. As Mueller puts it, the track record is that the U.S. military “is often incapable not only of defeating insurgents at an acceptable cost, but also of training locals to effectively defend themselves after the Americans have left.”

At the heart of this record of bellicosity is a problem of threat inflation. Even when faced with genuine dangers such as from the Soviet Union during the Cold War, the actual risks being faced have been wildly inflated by bad intelligence, political incentives, and an eagerness for saber-rattling. From the mythical missile gap to the domino theory, officials in Washington have long claimed imminent existential dangers that were later revealed to be wildly inflated.

Additionally, the United States in some sense overlearned the lessons of Japan and Germany, nations that under American occupation thrived with a quick return to liberal democracy. But the historical circumstances that made that possible have not applied elsewhere, from Vietnam to Iraq. Democratization by the might of the U.S. military has been a chimerical fantasy used to justify catastrophically failed wars.

The purported missile gap of the late 1950s is another telling example. American intelligence and military officials, as well as politicians like presidential candidate John F. Kennedy, expressed the need for a massive arms buildup to catch the supposedly advanced fleets of Soviet missiles aimed at the United States. One report, Mueller explains, “projected that the Soviet missile strength in the early 1960s would stand at 700.” In fact, “the actual figure turned out to be four, though the Air Force continued doggedly to suggest for a while that barn silos, medieval towers, a Crimean War memorial, and various mysterious-looking buildings in isolated areas were actually cleverly disguised missiles.”

Decades later, the same sort of threat inflation resulted not only in the waste of billions of taxpayer dollars but also in thousands of American military members’ lives and hundreds of thousands of civilian lives. The 2003 invasion of Iraq was premised on not only bad intelligence but even worse understanding of Saddam Hussein’s regime and its goals, foremost of which was mere survival after the total defeat of the 1990–91 Gulf War.

After the 9/11 attacks in particular, “fears about rogue states and about the proliferation of weapons of mass destruction were much enhanced by fancies that such states might one day decide suicidally to hand over some of their precious and potentially traceable arsenal to terrorists—irresponsible groups they could not control.” This theory was not only factually erroneous about Hussein’s actual arsenal of weapons but also about the plausible actions he might take even if he did have such weapons.

The Stupidity of War, published by the presitigious Cambridge University Press, is available from major booksellers and at Cato​.org/​books.