Each department/command is given a budget for each fiscal year, if they don't spend ALL of that budget, whether they need it or not, the next time a budget is set, it is lower than before.
Oh but if that were the only problem.
But no, it's worse. There are Soldiers all over Afghanistan doing without stuff. All over, there are Soldiers with shitty conditions that could be upgraded. But they wont be upgraded because top dogs are too busy thinking up shite they want to spend money on that makes THEIR area more awesome.
Dude, if I could itemize the shite that is being spend on that has ZERO to do with the war effort and ZERO to do with making Joe's life better, you'd barf.