It is actually easier than you think, you don't have to control too many humans to get us into an apocalyptic war, Just pinpoint a few world-leaders and they will get the things sorted out for you.
Step 1: Select a few nations that are powerful and are usually against each other. (US, China, Russia for starters).
Step 2: Select the political leaders (just the top ones), some influential media houses, and the intelligence agencies.
Step 3: Make them feel like the enemy are at the gates (not literally) and are about the launch of an all-out attack.
Step 4: A few false memories here and there, a few accidents at key locations (like a distant air-base), a missing nuclear submarine should do the trick.
Step 5: Just relax, our leaders will do the rest for you, But don't forget to make minor adjustments if and when required.
Step 6: Come for cleanup of whatever left when its all over.