For more than 50 years, U.S. national security strategy has undergone cycles of strategic retrenchment and renewal. After World War II, the United States rapidly demobilized, giving the Soviet Union and its proxies like North Korea an opening for armed aggression. By the end of the Truman administration, America had begun an extensive military buildup and a significant expansion of its alliances and security commitments. Another round of retrenchment came after Vietnam; once again, renewal followed. Under the leadership of President Ronald Reagan, defense spending increased, and the military fielded an array of new weapons systems and developed innovative doctrine and concepts. While the armed forces shrank under Presidents George H.W. Bush and Bill Clinton, there was no real strategic retrenchment—the United States expanded its global commitments, solidifying its role as the "indispensable" nation. The decade after Sept. 11 saw U.S. security commitments grow and a rapid expansion of the military and defense establishment.
Now the historical pattern seems to be holding. The United States has again begun retrenchment: disengaging from a major role in Iraq and Afghanistan, slashing defense spending and beginning to cut the armed forces. The Obama administration's 2012 Defense Strategic Guidance instructed the military to stop preparing for large-scale, protracted counterinsurgency operations. What has not happened, though, is any diminution of America's security commitments or disengagement from parts of the world. The mantra is to do as much as before but do it with less. Policymakers, military leaders and national security experts contend that if the Department of Defense becomes more efficient, if allies and partners substitute for a shrinking U.S. military and if future presidents make smart choices, the United States can retain its global influence on the cheap. Unfortunately, history and logic suggest otherwise.
One of the big problems with influence on the cheap is that, as military experts often phrase it, "the enemy has a vote." If the United States denudes itself of the capability for a type of conflict, that is exactly the conflict America's enemies will try to pursue. And as Libya and Syria show, today's world is so deeply connected that violence has cascading effects, destabilizing entire regions. Conflict can no longer be cauterized and ignored. When faced with an insurgency that threatens U.S. interests, a future president is less likely to stay out than to throw an undersized and inadequately prepared military into the fray. It is not hard to imagine the results.