With his Monday speech committing to the US to a continuation and escalation of the Afghan War, an already major increase in military spending for 2018 looks like it might be growing even more to cover the added expenses of a bigger conflict.

There is no good figure available on the cost of the first 16 years of the US war in Afghanistan. Estimates are that $1 trillion has been spent so far, between direct spending on the war itself and medical costs for Afghan War veterans.

That’s likely to just be a fraction of the overall cost, just for those 16 years, as the cost of caring for those veterans for decades to come will continue to mount. With little documentation for exactly where the money goes, the long-term costs of those 16 years are even more uncertain.

But turning that 16-year war into a 20-year war, or 24-year war, will have a predictable outcome. The costs are likely to be even harder to document, with President Trump keeping troop numbers secret. In the end, the bottom line will be more.

And potentially a lot more. The Afghan War is already America’s longest war, and it’s not like the front-line troops from 2001 are still the front-line troops of 2017. This effectively means the US is on the hook for major veterans expenses for multiple generations of troop rotations into and out of Afghanistan, and the longer the war lasts, the more veterans there will be.

While President Trump maintains that his Afghan War commitment is not “a blank check,” it might as well be. The US is already committed to an unfathomable amount of money for the amount of Afghan War already fought, and as Trump drags on the conflict the rate at which the money disappears will continue to mount. There will never be a literal ledger where someone writes in a final war cost, but those costs are very real, and will be felt for many decades to come.