Board Thread:Naruto Discussions/@comment-27556034-20160109145730/@comment-734582-20160109151744

Jitoul Nazuto wrote: how did madara survived after his battle with hashirama in final valley? Mangekyou Sharingan allows the user to create techniques that work after a certain time, even after death. Itachi used this to plant his Amaterasu in Sasuke's eye, to activate when seeing Obito's eye. He also did the same for Sishui's eye in the event it saw his own pattern.

Madara did the same, but using Izanagi. The effect didn't kick in until well after his death/defeat, so Hashirama didn't realize Madara's Izanagi undid his death.