The Zombie War was a massive pandemic released from the Cursed Realm by the Dark Army. The Dark Army soon joined the war themselves after the Ninja had defeated them. This caused the war to become the largest in history in which both sides fought to reclaim the ruins in order to rebuild the world as they wished. The war ended in the Battle of New Ninjago City in which the Ninja's army won the war.
The war began when the Dark Army launched their zombies into the west coast of Ninjago. They infected hundreds of thousands of people and advanced east. The Ninja tried to push them back but they couldn't for they didn't realize that the people they were trying to convince to stop were already dead and the virus was the only thing alive anymore. Soon the New Ninjago City Mayor decided to board up the capital city and prepare to hold off the virus. By the time the virus reached New Ninjago City nearly six billion zombies were within the Dark Army's control. The city fell within moments.
The massive zombie hordes eventually reached the Corridor of Elders where the Ninja and the Alliance of Elements held the zombies back for days until Ninjago Militants were forced to kill the zombies. This entered the war into it's violent phase. Now deaths began to occur. New weapons were developed such as the Laser Rifle from an upgraded version of the kind used by the Nindroids. The zombies were eventually wiped out and the Dark Army attacked themselves.