True
"If a small country declared war on us, we could easily bomb them back into the iron age."
Putin probably thought the same about Ukraine.
Military objectives were achieved in Afghanistan, but not in Korea and Vietnam. And based on Clausewitz: "War is politics by other means" And our politics changed....
Hard disagree on Korea. South Korea is a hell of an ally, very inconvenient for the PRC.
The objective of the US once they pushed back the initial invasion in the Korean War was to destroy the DPRK, force communism out of Korea, and unify the country. They failed. The war became a stalemate once China got directly involved.
If Vietnam becomes a stalwart ally of the US over the next 20 years that won’t mean the Vietnam War was a success just because the US ended up eventually having a useful interest in the region.
The objective of the war was to prevent the spread of communism. That goal was achieved.
> Putin probably thought the same about Ukraine.
I doubt, as Ukraine is far from being a small country. It is the second largest European country (counting Russia as an European country, as is common in geography). (he most likely had other miscalculations leading to the current situation)