There’s a tendency in Washington to compartmentalize every problem and to ignore the ramifications that policy toward one adversary can have upon others across time and distance. President Ronald Reagan’s decision to withdraw peacekeepers from Lebanon in the wake of the 1983 Marine Barracks bombing, for example, helped convince a young Osama Bin Laden that he could drive the United States entirely out of the Middle East, if not defeat America entirely.

President Barack Obama’s decision to impose a timeline on the U.S. presence in Afghanistan likewise convinced not only the Taliban but also insurgents and Shiite militias in Iraq that the U.S. did not have staying power.