I don't think you are morally obliged to do this. You didn't steal the money or make the decision to steal the money. You may have benefited from theft, but if so, the benefit did not amount to your entire salary, but to the difference between your net salary and your opportunity cost of working in the military.
Of course, if you want to do this anyway to make a statement, I don't see anything wrong with that. But in that case, you should simply arrange it in a way that is most convenient for you.