Russia’s intervention in Crimea also came just days after the Department of Defense proposed a 2015 budget that would reduce the U.S. army to its smallest size since before World War II. The budget is a recognition that the U.S. has been spending too much on its military for decades and will no longer be at war for the first time since 2001. It is also a much larger recognition that a debt-ridden, sequestered America cannot be expected to militarily enforce the interests of every ally in every corner of the globe.

Despite this, the rest of NATO continues to operate as if the full force of the U.S. military is behind it. In the interest of rectifying the massive imbalance within NATO, its members agreed in 2006 to each spend at least 2 percent of their GDP on defense (the U.S. typically spends around 4 percent). As of last year, only seven members met that mark. In fact, since 2010, most European countries’ defense expenditures have actually fallen between 8 percent and 30 percent.

That imbalance was apparent during the 2011 intervention in Libya. After the U.S. moved into a “supporting role,” the NATO countries maintaining the no-fly zone quickly began to run out of precision bombs, and the U.S. was forced to provide 80 percent of aerial refueling. In a preview of his post-retirement candor, Secretary of Defense Robert Gates warned at the time of “a dim, if not dismal future” of “collective military irrelevance” for NATO if trends continued.