A U.S. withdrawal from the task of promoting world stability not only results in war and unspeakable suffering, as in Syria, but it also degrades the performance of the global economy. The threat of terror is, of course, very bad for local economies: It discourages tourism and keeps people away from crowded restaurants and sporting events. But its effects are also global, according to the 115,000-member Chartered Institute of Procurement and Supply (CIPS). CIPS tells the FT, “the rise of radical Islam in the Middle East and the reintroduction of border controls in Europe is disrupting supply chains and raising costs for business.” CIPS values the added costs in the billions, saying that the effects are multiplied in an economy already hit by unstable commodities prices and Russian aggression.Officials in Washington should not only see fighting terrorism abroad as a protection against attacks at home. Terrorists are also a threat to the global economy, the stability of which is a necessary ingredient for American companies and American world order. By letting ISIS establish a presence in Syria and Iraq, the U.S. has perhaps cost an already-fragile global economy billions of dollars. Isolationism and American withdrawal from the world is a mistake.