As we all know by now, Madara broke free from the Edo Tensei. This got me thinking on how he knew the signs. Seeing as how Tobirama created the technique, it made me come to the conclusion that he used it to bring back Izuna. It was possibly done to help the alliance between the Senju and Uchiha or to keep Madara in check. Thus causing Madara to try to rebel with the Uchiha. It's true, without their support he left the village. However, I believe before he left Tobirama undid Izuna from the Edo Tensei with which Madara copied the relase seals. I know it's a long stretch but please tell me what you think.