[notahacker]

The politics define what 'victory' is though.

I mean, politics defined the objective for Vietnam as limiting the spread of communism and proscribed the only way in which the US could certainly have achieved that objective and 'won' the war militarily (nuke the entire population). So yes, it defined the terms of their failure, but I'm not sure one can meaningfully claim victory without politics anyway. Politics also defines the temporary grounds on which the US can be said to have enjoyed temporary and limited success (enabling a separate South Vietnam to persist whilst they were present, considering South Vietnamese losses tolerable in context)

But the military element is clearly a large part of that political failure. The US military didn't feel they could win the war on the terms they'd been given without calling up 2 million conscripts, and couldn't eliminate the Viet Cong quickly enough for the public to tolerate this, with military setbacks like the Tet Offensive strongly influencing the political shifts.