Ok, So Indra and HAgoromo are both partly to blame for the Uchiha vs Senju wars. However, it was Hashirama they fixed all that and still screwed up. You can say that Madara is the one to blame, but he only turned evil because the shinobi system is bullshit, like everyone else.
If you think the shin obi system, which hashirama set up, is good, explain to me how they managed to start a world war within 1 generation, and have a second one after that, and then a third, and now a fourth, without a single generation getting a break.
To illustrate how close they have been together, Tsunade has fought in 3/4 of them, that we know of..
We know she is in the 4th, and the second one is when she fought Hanzo. 3rd is between the two so it is presumed that she was a medic.
Since Tobirama fought in the 1st, and Tsunade was around before hashirama died, She was probably there too, but not fighting.
If one girl gets to see 4 separate world wars, you know the shin obi system is shit.