Back in 1993 we had a rule for Nuclear Weapons.
First you had to discover it, but could not do so until after round 10 (classic, remember.)
Second, it had to be loaded on a heavy bomber
Third, it removed 50% of the units on a territory if the bomber lived through any AA Guns.
Purpose: Back then there was a problem of 400 infantry on Japan and it was just a pain to take it. This way we could eliminate all 400 of them with 2 nuclear weapons and assault the next round iwth infantry.