The whole basis of this article is that report by ThirdWay that uses “constant 2016 dollars.” However this is misleading because salaries for Pentagon employees aren’t paid in “constant 2016 dollars.” In real terms (i.e. constant 2016 dollars), base salaries for military personnel went up about 15–20% (depending on pay grade) from 1980–2011. That doesn’t even account for skyrocketing health care costs, which are now over 10% of the Pentagon’s budget (up from 6% in 2000). So our quantity/quality of forces isn’t necessarily much better than 1980.
Considering that the population of the rest of the world (i.e. our potential enemies) has nearly doubled since 1980, I would expect our military to have gotten somewhat bigger. Particularly since our closest allies are much less able to help us today than they were in 1980.
The American economy is 2.5 times larger, in real terms, than it was in 1980. The fact that military spending hasn’t even doubled (i.e, is less than 100% bigger) is evidence that the Pentagon’s influence hasn’t been able to prevent de facto cuts to its capabilites.