The Department of Defense, not counting the cost of the war in Afghanistan and the last bit for Iraq, which is separately budgeted, spent around $530 billion last fiscal year (3.4% of calendar year 2012's estimated GDP, note the calendars don't quite overlap). That's out of an estimated $3.54 trillion budget, or about 15% of the budget. Even the claim that this is "almost 50 percent of federal tax monies" (we are of course also borrowing more than a trillion dollars a year) is incorrect, the estimated FY2012 tax revenues were $2.45 trillion, putting the DoD at 22% of them. Even if you add in the costs of the wars the number don't change much.