Charles Kenny argues that we are safer than ever:

As Tufts professor Michael Beckley points out, the U.S. now "formally guarantees the security of more than 50 countries," which means the U.S. has more allies in the world than at any time in its history. More broadly, war between nation states has been incredibly rare since 1945. Europe is the most obvious beneficiary of Pax Americana: Before today, the last time the Rhine had gone this long without being crossed by armies with hostile intent was more than 2,000 years ago, according to economic historian Brad DeLong. The painful and often violent process of building independent nation states out of colonies was often stoked into civil war by the competing powers of the Cold War. But with the decline of that global struggle, and the growing legitimacy of the new countries, even civil wars are on the wane.

He believes that sustained peace among great powers is making military cutbacks more palatable:

In Harris polls since 2008 the percentage favoring defense cuts has risen from 35 percent to 42 percent. Of five areas of expenditure—Social Security, Medicare, food stamps, Medicaid, and defense—the military was only area where a majority (60 percent) suggested spending should be cut to reduce the deficit.