I noticed in my recent attacks on a continent with 96 ICBMs that it only takes 2 ICBMs in a single turn to eradicate all and every unit currently inside a city...
no matter the size of the stack inside a city, simply launch two ICBMs at the target and watch the stack be destroyed 100% every time.
no matter the size of the stack inside a city, simply launch two ICBMs at the target and watch the stack be destroyed 100% every time.