I'll admit it's literally been a few decades since I took the oath, but the way they write things these days wouldn't this be a breach of contract concerning this?
This was/is one of the ways they get ppl to enlist, by offering a free education. If it's in your contract when you sign up... (IANAL)
As for those that say boo hoo you have to pay too, suck it. I may not agree where our govt sends our troops but they're still our sons & daughters.