The Atlantic: The Logic of Mission Creep

In 49 BCE, Julius Caesar traveled with his troops to the banks of the Rubicon river in northern Italy. By an ancient law, no Roman general was allowed to cross the river with an army. Caesar paused momentarily, weighing the terrifying prospect of civil war. Then, according to the Roman historian Suetonius, Caesar declared “the die is cast,” and swept south toward Rome. This week, President Trump struck a Syrian airfield with dozens of cruise missiles, following an attack by the Syrian regime on civilians with sarin nerve gas. Has Trump crossed his own Rubicon, and reached a point of no return, with the prospect of full-scale embroilment in the Syrian morass?

There’s good reason to think the air strikes will be an isolated event. After all, none of the key players in Syria have an interest in triggering a major conflict. Bashar al-Assad is winning the civil war. Why snatch defeat from the jaws of victory by taking on the U.S. military? Meanwhile, Trump has long pressed for getting out of wars in the Middle East, and focusing on nation-building at home. Similarly, Russia has no desire for a larger contest against the United States. Trump’s proposed increase in U.S. defense spending is about the same as Russia’s entire defense spending. Trump reportedly received three options for a military strike, and chose the most limited. All of this suggests that cooler heads may prevail.

But the history of recent U.S. military operations shows how missions can morph unexpectedly into larger endeavors. “Once on the tiger’s back,” warned Undersecretary of State George Ball about U.S. intervention in Vietnam, “we cannot be sure of picking the place to dismount.” America’s recent big wars—in Afghanistan and Iraq—were supposed to be speedy regime change operations, but both turned into costly and prolonged counter-insurgency campaigns. Smaller-scale peacekeeping and humanitarian operations, which might seem more analogous to the Syrian strikes, were also subject to mission creep.

For example, the U.S. intervention in Lebanon in 1982 began as part of a multinational effort to oversee the withdrawal of Syrian and Palestine Liberation Organization (PLO) fighters from Beirut. This mission went smoothly, but the goals broadened and the United States became an active player in the Lebanese civil war—until a suicide bomber struck the marine barracks and killed 241 Americans. Similarly, the humanitarian mission in Somalia in 1992 started out as a limited operation to deliver food but shifted into a broader nation-building operation to stabilize war-torn Somalia—a road that led to the deaths of 18 Americans in the “Black Hawk Down” battle.

Of course, these interventions all involved U.S. ground troops from the start, so what about bombing campaigns? Again, the tiger’s back often proved a bumpy ride. 

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Associate Professor of Political Science Dominic Tierney, a senior fellow at the Foreign Policy Research Institute, is a contributing editor at The Atlantic and the author of three books, including How We Fight: Crusades, Quagmires, and the American Way of War (2010). Tierney completed his Ph.D. in international politics at Oxford University in 2003 and was a post-doctoral fellow at the Mershon Center at Ohio State University and the Olin Institute at Harvard University before joining Swarthmore's faculty in 2005. In 2008-2009, he was a research fellow at the John F. Kennedy School of Government at Harvard.