Over on the White House website there is a way to look at the way taxes are divided among major spending categories. You can check in HERE. Or just look below. You have to scroll around a bit.
Now here is the rub. Actually only one of several. The items "National Defense" and "Veterans Benefits" account for 30% of the total. We are in two wars and party to a new one in the making, none of which can be easily understood as being about National Defense. In the two wars we have been at least as offensive as defensive. Libya is another story, but it is one yet untold. It is hard to call our efforts there matters of national defense. Better call it what it is: the support of revolution when it suits our interests. Still, taking the two wars, and the actual needs of National Defense, 26.3% straight out, and 4.1% for those who serve in these wars (and others) is a big piece of the pie. No doubt there are other costs hidden in other parts of the budget and the mounting interest payments on debt - not to mention paying off the debt - to be considered. So, what happens if we divide the pie a bit more and separate out the costs of the two wars, and make that piece "National Offense" rather than "National Defense"? Not a pretty sight.
Go on the site and look around.