Much of what I've read (not primary sources) implies that, at least so far as the UK is concerned, after a nuclear attack has happened the Government planned for contingencies and recovery of society. For example: http://www.bbc.co.uk/news/magazine-29804446
I'm aware of civil defence contingencies, but there seems to be an absence of any suggestion that a military threat would remain and an implication that there would be a cessation of hostilities. Was that really the case? Or did governments and militaries on all sides plan for a continuation of military action after the use of nuclear weapons? If so, what were the likely objectives and what was planned for the vanquished opponent(s)?
Sadly we just don't know as we only have the limited civilian files to go on, all the military stuff is still classified (and probably will always be). Indeed a mid 1960's UK government exercise simulating the lead up to a conventional conflict simply stops at the moment of the government considering itself to be at war.
For post-nuclear military planning we have no idea though there was a plan in the late 40's by the US to occupy the USSR after a nuclear strike. The plan was based on incredible outdated/ stereotyped assumptions that communist rule would simply collapse once Moscow was destroyed and the general population revolted. The US would then move in an govern the country with the help of white Russian exiles. Though given the plan required 400 nuclear bombs when the US only had 50 (even Truman didn't know the true number) this wasn't the most serious flaw.