"$300 Million a day on Afghanistan" - so what happens to that money now?

Question

President Biden, in his speech regarding the conclusion of the withdrawal from Afghanistan yesterday, mentioned that it is estimated that 300 million USD per day was spent on the war in Afghanistan over the past 20 years (that's 109 billion USD per year).

Now, sure, the spending is not uniform over time. But - let's say that until the decision to withdraw only 20% of that figure (22 billion USD) was being spent annually (completely speculative assumption of course).

So what happens with the 22 billion USD / year the US will now not be spending on Afghanistan? Is it just un-utilized appropriations? Is it swallowed by the un-auditable belly of the Pentagon (and the CIA/USAID budgets etc.)? Is Congress accounting for this in budget discussions?

Answer 1

So what happens with the 20 Billion USD / year the US will now not be spending on Afghanistan? Is it just unutilized appropriations?

Maybe, sort of, not really. Under the Impoundment Control Act of 1974, the President cannot unilaterally decide to stop spending money which Congress has validly authorized. On the other hand, the President is the Commander in Chief of the US Military, and does have the right to make operational decisions such as withdrawing from Afghanistan. In theory, I'm not sure exactly what happens to the money when those two rules come into conflict, but I am very skeptical that Congress can override one of the President's core Constitutional functions with a mere statute. In all likelihood, the money is either supposed to be explicitly rolled over into the Pentagon's general budget, held in some sort of "just in case we decide to go back" fund, or returned to the Treasury, depending on how Congress worded the appropriation. However...

Is it swallowed by the un-auditable belly of the Pentagon?

In the short term (in theory: for the rest of the fiscal year, which ends in exactly a month on October 1, 2021, but in practice until Congress actually passes a budget, which generally takes many further months), this is the most likely outcome. The Pentagon's budget is notoriously opaque and repurposing appropriations in this fashion seems to be standard operating procedure, albeit of dubious legality.

Is Congress accounting for this in budget discussions?

Of course. But that's trivially true, because Congress accounts for everything in budget discussions. Or at least, every major political issue, anyway. That doesn't mean they're going to substantially cut the military's budget, however. In absolute terms, the US has the highest military spending in the world, and cutting military spending is politically fraught. Probably there will be some political haggling, and the end result is that there won't be a line item for "Afghanistan" anymore, but spending on other items will be increased to at least partially make up the difference. It's difficult to speculate any more specifically than that.

Answer 2

What should and possibly even might happen is that the US military refits for a major theater war after all these years of counterinsurgency.

Remember all those MRAPs they purchased for Iraq and Afghanistan? High profile with lots of ground clearance to survive mines, armed mostly with machine guns. Not the thing to deter Russia or North Korea. (Getting into a ground war with China would be foolish, that contingency calls for the Navy and Air Force. Who have their own funding priorities.)

Here an overview for the Army wishlist.