Here is my scenario .
Asia ,Africa ,Australia ,and Both Americas are destroyed by a vicious Nuclear exchange .Europe is left largely intact but satellites are`t working .The whole global communications network is not working .And the continent has no access to oil ,enough food to support it .
Now what happens in the century after ?Do the Europeans manage to maintain the current level of technology .Or are they stuck in the 17th century ?
Also since the nations comprising Europe will most certainly establish martial law .Do we see an eventual turn to monarchy after a while .Also would Democracy be blamed for the war ?Kind of a to many people had power to rule with any sort of sense .