Board Thread:Naruto Discussions/@comment-26773508-20150905054531/@comment-26275777-20150907122709

Thekillman wrote: I don't know the full extent of Hiruzen's knowledge of the Uchiha. However, he must've been aware of Sishui's Mangekyou Sharingan. He might have believed that an Uchiha awoke his own MS with the powers that fit the masked man. But i think this piece of information, that is which uchiha could've done this, might've led to a lot of problems for Hiruzen.

That's why I said "or more likely were secretly raising someone like him". It's certainly rather suspicious that suddenly young Uchiha children were developing the Mangekyou through no apparent means (Shisui). No wonder they pulled him into ANBU - keep your enemies close and all that.

Although Madara was the only one known to be able to summon the Kyuubi, so it's likely that Hiruzen would still have held the possibility in his mind.

I don't think Danzo is such an "all-knower" that he would be unsurprised of someone like Madara. I think it's more likely that to Danzo, all of this was just confirmation of his own bias against them. uchiha hiding their true power and all.

He doesn't need to be an all-knower to come to the same conclusion Minato did in about fifteen seconds. Powerful Uchiha who can control the Kyuubi and give the Hokage a run for his money (apparently) - you don't even need to connect that many dots. Bear in mind that he and Hiruzen actually lived in the same era as Madara did.