Wow I can't believe that noone would think of this. You are absolutely right.
This state = war, not in state of Edo Tensei.
"his" doing = this war is caused by him(tobi).
According to plan = to who's plan? Madara's or Tobi's? This is crucial for us to know so we can understand how come Madara knew about Nagato.
If they would be allies than Madara would have known what is his plan.
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Kabuto says he needs Sasuke, a living Uchiha, for his plan in discovering truth behind ninjutsus(probably becoming SO6P). It has something to do with his body and his blood. Madara also said something like "you have discovered secrets of my body..?"
There's still question to why Madara is attacking everyone. Is it because of the Edo Tensei auto-attack? Allied forces attack him first. Maybe Madara is just THAT badass that he won't allow anyone to fuk with him? He never was a good guy to begin with but he's not absolutely evil either. He probably doesn't care much for the allied forces.