The White House has a handy website to mislead you about your tax dollars at http://www.whitehouse.gov/taxreceipt 
It claims that only 26.3% goes to "National Defense". This is similar to the claim in the 1040EZ US income tax form booklet (see pages 36-37). Here are those two pages in a PDF . There the claim is that the U.S. government only spends 22% of its money on "National defense, veterans, and foreign affairs." The form admits that you could leave out the "foreign affairs" part and still be at 21%.
The White House website claims to calculate both veterans' expenses and foreign affairs separately and still put "defense" alone at 26.3%.
However, take a look now at the pie chart  created by the War Resisters League, which shows 51% of the budget going to the military.
21% and 26.3% and 51% aren't even close to each other. This is not "good enough for government work." This is our money. What gives?
Well, the White House website and the income tax form play a number of dirty tricks on us. The income tax form lumps Social Security and Medicare into the budget even though they are not funded with income taxes and are not discretionary spending. Take that money out, and the 1040EZ now tells us that the military makes up 32% of national public spending. But the White House website claims to be dealing just with income tax when it puts military spending at a mere 26.3%.
The tax form says it's using FY2009 numbers, while the White House says it's dealing with FY 2010, as does the pie chart. But the numbers haven't changed THAT much. The tax form and the pie chart are including veterans costs. Adding those in on the White House website gets us to 30.4%. That's a little bit more honest a number, but still a long ways from 51%.
To review, the 2009 tax form puts military and veterans spending at 32%, the 2010 White House website at 30.4%, and the 2010 War Resisters chart at 51%. Something still needs to be explained.
Part of the explanation is surely that a chunk of federal spending is payment of interest on debt, and most of that debt (80% according to the War Resisters League) is for past military expenses. Both the tax form and the White House website lump all debt together as something separate from the military. Applying the WRL calculation to the numbers on the White House website would bring its actual total military spending to 36.3%. That's a good bit more than the 26.3% any casual reader of the White House website will come away thinking goes to the military. But it remains far short of 51%.
I can't tell from the posted explanations, but very likely a couple of things are happening. First, we spend a great deal on military operations through departments other than the "Department of Defense." The State Department hires mercenaries. The Energy Department builds nukes. There's a whole new department called "Homeland Security." The CIA apparently has enough cash sloshing around that the President can secretly authorize it to arm a force in Libya sufficiently to take on another force we helped arm in Libya. The bulk of our "foreign aid" consists of giving weapons (or cash with which to buy U.S. weapons) to countries we may one day fight wars against. The War Resisters League seems to be trying to calculate all of these things. The White House probably isn't.
Second, even though the year 2010 has already happened, when its budget was originally laid out, it didn't include a "supplemental" (off the books) spending bill for wars. This is a nifty little gimmick the Obamabots inherited from the Bushies after having campaigned against it. I would be less than shocked if the supplemental was still being left out of the White House numbers as if it had never happened.
In addition, there is a fundamental problem of honesty on the White House website and in the income tax booklet. Both refer to the military as "defense," while most of the expense has absolutely nothing to do with defense. We build weapons for which no enemy exists. We build bases halfway around the globe. And the Justice Department justifies wars, such as the latest one in Libya, without even trying to claim there is anything defensive about it.
We are not spending 26% on defense. We are spending 51% on the military.
Learn more and act more: http://defundwar.org