How Tobi had strength to fight the fourth hokage!
I think I found out how, Tobi/Obito got the strength to fight Fourth hokage, at the young age of 13-15.
Alright, first off. Look --> : http://www.narutobase.net/manga/Naruto/596/15
Here we can see, that Tobi/obitos arm has been hit by a rasengan.
Yes. now look at this http://www.narutobase.net/manga/Naruto/503/3 <-- His arm was destroyed by a simple rasengan I think.. And we all know it was zetsu stuff dripping out, which would explain only one thing. ZETSU Saved obito! Zetsu must have merged with Obito, thats why he knew so much stuff, that would explain how the hell he was so powerfull in a young age.
And in the war, he must have gotten an arm sewed on like Deidara, its possible as we have seen with him. And I mean he needed zetsu to do the gorilla tactics and stuff in the wars, thats why he isnt " one " with obito. Giveing him chakra etc.