[KarlInOhio]

The Supreme Court case Flemming v. Nestor in 1960 made it quite clear that you do not have any vested rights to Social Security benefits. Congress can change them at will (under limitations provided by the equal protection clauses of the Constitution, i.e. they couldn't say everyone but Poundstone gets paid). They could even cancel the whole program tomorrow and tell the people who were expecting checks at the beginning of September "Stinks to be you!". Of course they could never do that politically, but there is no contractual obligation for them to pay them.

I don't know whether there is a contractual obligation to pay for military or civil service retirements. I wouldn't be surprised to see that there is no such contract with military retirees, or that it is pretty loose with a lot of "or such benefits as determined by Congress" exceptions in it.

[Tublecane]

“I don’t know whether there is a contractual obligation to pay for military or civil service retirements”

The problem with contracts with the government is that you’d have to sue to get them enforced, and the government runs the courts. They don’t like to be sued, and invoke a bastardized 11th amendment in their defense. Only civil rights cases routinely run the gauntlet.