The lesson of the past several decades is that once Americans establish ourselves to assure security, we stay as long as it takes and then stay some more. World War II has been over for 67 years, but we still have 37,000 troops in Japan and 53,000 in Germany.

At one time, these forces could be justified as a counterweight to the Soviet Union, but the Cold War is ancient history. The Korean War ended in 1953, yet 28,500 American troops remain in South Korea.

Going over the fiscal cliff may not be good for the economy, but it might have one valuable result: forcing Americans to reassess our enormous defense budget.

Taking $492 billion away from the Pentagon over the next decade wouldn't be hard to do if we forced other nations to take more responsibility for their own defense—and used the opportunity to reduce our overall troop strength. What's hard, and expensive, is our vast array of overseas commitments.