Great Cataclysm

The nuclear war which preceded the Great Destruction

The Flood of the Great Destruction

The Great Destruction is the apocalypse which transpired during the events of Shin Megami Tensei and heavily influenced the world in Shin Megami Tensei II, in which most of humanity were wiped out by giant floods, supposedly a form of punishment as delivered by God.

The series of events started with the rising tensions between a Japanese resistance force and the Provisional Martial Law Government set up by the American Army after the sudden appearance of demons in Tokyo. The head of the American forces was actually a disguised demon Thor, acting under orders from Law-aligned forces. He reveals himself to the Protagonist and his party before launching nuclear ICBMs at Tokyo to suppress the demon outbreak, destroying Tokyo in a nuclear holocaust.

Decades later, in a rebuilt Tokyo where demons roam freely, the Mesian and Gaian cults have formed. The Mesian forces of Law succeed to building a great Cathedral to bring forth God's Thousand Year Kingdom. This act causes a second Great Flood which again destroys Tokyo, leaving little standing apart from the Cathedral and its inhabitants.

Years later, after the Hero succeeded in toppling high-ranking members of both the Mesian and Gaian cults, the inhabitants of the newly-built Tokyo Millenium civilization (built upon the remains of the Cathedral), refer to these two disasters as The Great Destruction. Both disasters seem to be directly related to the actions of the Law forces.