The US is obligated, by treaty and policy, to provide mutual defense to most of the world. The US military has additional moral obligations to minimize civilian casualties, as well as political obligations to minimize both time expenditure and friendly casualties.
These requirements are historically unprecedented and contributes significantly to overall cost. In the 1990's, the US and NATO managed to put an end to ethnic cleansing in the former Yugoslavia through direct military action without incurring any significant casualties. In 1991, the UN-mandated Persian Gulf War incurred so few friendly casualties, it was statistically safer for coalition troops to serve in the Persian Gulf than to stay at home simply because the added casualties from combat were less than the reduced casualties from car accidents.
In any case, there's a much better way of overlapping the two: require 2-4 years of national service and then designate the basic income guarantee as a veterans' benefit. (It wouldn't have to be military as there would be other options for conscientious objectors). This would increase military manpower, make it less likely to go to war unnecessarily, reduce youth unemployment, provide near-universal job training to reduce unemployment in the long run, solve the college debt problem via the GI Bill, and reduce social stratification by throwing everyone into the same situation early in life. And if you don't want to do it, then you don't get basic income and you don't get to vote. But that would never happen.