The war with Iran is an epic disaster. The United States and Israel launched an unnecessary campaign that has violated international law, killed at least 1,700 Iranian civilians (including 307 children), caused widespread damage to civilian infrastructure, and deepened regional turmoil. Iran’s retaliation has killed 18 U.S. troops and injured more than 600 on bases in neighboring countries, and people around the world are still reeling from the spike in energy prices caused by the closure of the Strait of Hormuz.

This war is the latest consequence of a series of U.S. policy choices over the last 35 years that have made the United States less safe and intensified conflict across the Middle East. Those failures stem from the U.S. military presence in the region, which has fed Washington’s mistaken belief that it must continually launch wars and intervene in ongoing conflicts to advance U.S. security. Welcoming American bases and troops onto their territory has also made host countries more vulnerable, exposing them to direct attacks from Iran and Iranian-backed groups.

For decades, the United States has acted as though its military presence in the Middle East were essential to American strategic interests and regional security. It has sought to protect partners such as Israel and the Gulf states, check Iran and other adversaries, and combat terrorism. In practice, the U.S. military posture has contributed to instability and destruction. Nowhere is this clearer than in the campaign against Iran; the war has generated the very dangers it was meant to prevent.

It is long past time for the United States to withdraw its forces from the Middle East, stop arming governments that violate U.S. and international law, and end its role as guarantor of regional order. Doing so would free Washington to concentrate on higher-priority objectives, including deterring great-power war in Asia and Europe.

Although the United States has long been engaged in the Middle East, the Gulf War of 1990-91 cemented the U.S. military role in the region. What started as the high point of post–Cold War American power—organizing an international coalition to end Iraqi President Saddam Hussein’s invasion of Kuwait—turned into a decades-long obligation. Successive administrations have kept tens of thousands of personnel in the region, believing that a standing force would protect the free flow of energy, support Israel, combat terrorist groups, and deter Iran. Currently, about 2,000 troops are stationed in Iraq; 2,300 in Saudi Arabia; 3,500 in the United Arab Emirates; 4,000 in Jordan; 8,000 in Bahrain; 10,000 in Qatar; and 13,000 in Kuwait. The precise numbers and locations have ebbed and flowed over the years, but that presence has remained enormous, sprawling, and deeply embedded.

Yet a military footprint can itself become a liability, exposing host countries to reprisal and drawing the United States into local conflicts. With bases scattered across the region, threats to American interests are constant, and each one becomes a new argument for enlarging the footprint. The United States’ occupation of Iraq after the 2003 invasion, for instance, not only mired U.S. forces in a long and bloody conflict but also made them vulnerable to Iranian-backed militias, prompting retaliatory U.S. operations in Iraq, Syria, and elsewhere. Meanwhile, the war in Afghanistan spilled into Pakistan, where the United States carried out hundreds of drone strikes against militants attacking American troops across the border. After largely extricating itself from Iraq in 2011, the United States had to send troops back in 2014 to fight the Islamic State, or ISIS, which emerged from the post-invasion chaos.

The cost has been steep. The United States spent $8 trillion fighting in Afghanistan, Iraq, and other theaters as part of its post-9/11 “war on terror.” According to research at Brown University, roughly three million Americans........

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