"We have to look at whether [US military aid] even succeeds in giving us benefits," says Christopher Preble, author of "The Power Problem: How American Military Dominance Makes Us Less Safe, Less Prosperous, and Less Free." Less ambiguous, he adds, are the costs: "what we have paid – in tangible dollars, and in terms of our values."
The Pentagon, not surprisingly, hopes for a big return on its investment: a bulwark against communism during the cold war, for example, and against terrorist extremists after 9/11. The hard truth is that such aid is, at best, a lever that can be used to try to push a strategic ally – say, Pakistan, Turkey, Egypt, or Yemen – to take greater account of US wishes than it might otherwise, many defense analysts say. And it doesn't always work, they caution.
"The expectation has always been that countries that receive US military aid and training will be bulwarks of stability and will further US interests in a particular country or region," says Ted Galen Carpenter, vice president for foreign-policy studies at the libertarian CATO Institute. "Those expectations have often proved excessive."
If military aid buys less influence than the Pentagon imagines, it can still have value. During the recent uprising in Egypt, Pentagon leaders urged their Egyptian counterparts to exercise restraint against protesters – and they did (though perhaps for reasons of their own). Moreover, US law requires that aid be cut off if the recipient nation is using it to commit human rights violations – another leverage point.