President Trump is wrong to precipitously withdraw U.S. troops from northern Syria. That doesn’t mean he’s wrong about his overall point that the United States is involved in too many conflicts that are peripheral to our national security.

Trump’s withdrawal is wrong for all the reasons the foreign policy establishment says it is. The United States should not abandon allies such as the Kurds, especially when that ally has done the bulk of the hard and costly ground war against the Islamic State. We have an interest in keeping Iran and Russia from using Syria as a forward base from which they can destabilize friendly regimes across the Middle East and threaten Israel directly. Without some U.S. military presence in that area, the Islamic State or another radical Islamist organization could rise and again seize territory to launch terrorist attacks against the West. Withdrawing troops with neither warning nor planning does nothing to strengthen U.S. security and a lot to weaken it.

None of that means the establishment’s preferred foreign policy is optimal. In reality, the United States is committed to a global military and alliance structure that is proving increasingly difficult to manage or finance.

Current U.S. policy was constructed during the Cold War to combat the threat from the Soviet Union. The ambitions of the Communist government, given the impoverishment of almost every other industrialized nation after World War II, meant the United States had to assume a leadership role to preserve global freedom. U.S. leaders created a large peacetime military for the first time in history and crafted permanent global alliances as well. The cost was high, with U.S. defense spending averaging close to 10 percent of gross domestic product between 1946 and 1948 and well over 6 percent of GDP until the fall of the Berlin Wall. But it was worth it, as the Soviet Union ultimately bankrupted itself trying to keep pace.

In retrospect, however, it was easy to contain and defeat the Soviets. The U.S. economy dwarfed theirs at least two-fold throughout the Cold War. Combined with Western Europe and Japan, whose economies together exceeded our own, our alliance system presented the USSR with a contest it could not win.

None of these factors remain true. The economy of our major adversary, China, is larger than ours on a purchasing power parity basis. Russia’s economy remains sizable, and regional powers such as Iran retain significant economic strength. Meanwhile, U.S. defense spending has dropped and is now roughly 3.2 percent of GDP, although that total probably excludes money spent on nuclear weapons and our intelligence operations. Our allies’ defense spending has dropped through the floor, averaging well below 2 percent of GDP with only a few countries such as the Britain, France, Israel and South Korea above that level. The U.S. military remains the world’s most powerful, but it is significantly smaller than it was during the Cold War.

Our global commitments, however, have increased during that time. The United States had no systematic combat deployments in either the Middle East or Central Asia during the Cold War. Today it has troops in Syria and Afghanistan, has spent well more than a trillion dollars in Iraq and has frequently one or more carrier battle groups stationed near the Persian Gulf. According to the State Department, the United States is bound by treaty to come to the aid of 53 countries — not including Israel, which no one thinks we would abandon in case of war. We are simply defending more with less despite growing and increasingly aggressive foes.

This imbalance between U.S. commitments and U.S. power should force policymakers to rethink our objectives. If maintaining our current level of engagement and commitment is in the national interest, then defense spending must increase dramatically. Mutual commitments will also likely have to come with mutual levels of effort; the United States ought not to be spending scarce resources defending nations that will not make a commensurate effort themselves. This surely would be the optimal course.

But if neither is in the offing, then it behooves the United States to start slowly unwinding commitments it has neither the will nor the capacity to fulfill. It will harm the United States much less to withdraw from Afghanistan than it would to be unable or unwilling to respond to an invasion of an ally such as Estonia or South Korea. For all of his bluster and foolishness, Trump sees this while most others remain frozen in our past.

Empires rarely fall all at once. Instead, they weaken as their power fails to match their ambitions and they lose control of the peripheral portions of their realm. The United States has the most benign empire the world has ever seen, but it has one nonetheless. If it fails to rethink its strategy soon, expect it to begin losing some its peripheral allies in the not so distant future.

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