With just 20 days left in office, Gates lashed out, speaking directly to partner nations in Brussels, accusing European allies of dumping the majority of their military burdens onto the laps of the United States. He warned NATO that it risks becoming a relic the United States can no longer afford.
"The blunt reality is that there will be dwindling appetite and patience in the U.S. Congress -- and in the American body politic writ large -- to expend increasingly precious funds on behalf of nations that are apparently unwilling to devote the necessary resources or make the necessary changes to be serious and capable partners in their own defense," Gates said.
He pointed to Libya as a prime example.
"While every alliance member voted for the Libya mission, less than half have participated at all, and fewer than a third have been willing to participate in the strike mission. Frankly, many of those allies sitting on the sidelines do so not because they do not want to participate, but simply because they cannot. The military capabilities simply aren't there."
The United States pays more than 75 percent of the defense budget for the 28 members of the North Atlantic Treaty Organization. Gates said that by slashing their own defense budgets, the European nations are falling short in Libya.
"The mightiest military alliance in history is only 11 weeks into an operation against a poorly armed regime in a sparsely populated country, yet many allies are beginning to run short of munitions, requiring the U.S., once more, to make up the difference," Gates said.