Actually, the DoD has funds specifically apportioned for it for thenfirst time in a Decade.
Most of the funding apportioned to the DoD is equally locked in for various projects and tasks. That said, they do have a small amount of funds that are unapportioned and as of current unnaccounted for that the President is raiding. Typically these funds are meant for unexpectwd events that come up, unexpected costs arising, etc. that gives the Department (and others) a small slush fund to work with if the need arises rather than go and beg Congress every time they need a small amount of money.
So basically, the President is raiding various departments rainy-day funds. At the start of thebyear, meaning that any issues that arise through the year will have no funding available for them.
I am going to guess he gets little resistance this year, but I doubt various agemcies will be pleased when it happens again next year.