As an Uchiha, Madara possesses an innate hatred for the Senju clan,  as what is known as the Curse of Hatred , which dates back to the early days of the ninja world. This curse led him to oppose the truce fearing that his clan would be oppressed by them, and when Hashirama was selected to be Hokage instead of Madara, he defected from Konoha and attempted to attack the village after failing to replace him. His animosity towards Hashirama was particularly strong, going as far as to forbid Ōnoki from mentioning that name in front of him ever again. Nevertheless, Madara possesses a high level of respect and admiration for Hashirama as well as the Senju name as seen during the Fourth Shinobi World War where he would praise and curse Hashirama or other members of the clan in the same breath.  Conversely, he also lamented that he would have taught Hashirama how to resurrect himself if he had known how much weaker the modern day shinobi would be compared to them.  Madara was very competitive with his younger brother, Izuna, but Tobi also implies that Madara and Izuna were close as brothers.