After WWII, the modification of 'unconditional surrender' allowed the Japanese to keep the Emperor. His declaration of surrender was absolutely invaluable, and he sent his family to China and Manchuria to convince the troops to give up. The country rather docilely submitted to MacArthur's rule even though there were military people who absolutely wanted to continue the fight.

In Germany there is a conflicting history, but apparently there was no significant insurgency. Also, there were no foreign nations willing to arm or supply an insurgency.

Now, especially in the Middle East, all it takes is one of the current superpowers to be willing to arm an insurgency and it will go on for a long, long time. The US, China, and Russia cannot prevent any one of them from arming an insurgency. And soon India will also be a 'big' if not superpower, able to influence events without fear of reprisals.