Originally Posted by uzumakinagato
Of course Madara and Tobi know each other. Madara talked in a chapter aswell about the moon's eye plan.
Not only that but when Kabuto was speaking through Muu he spoke of assisting HIM. Madara seemed to acknowledge / understand without question who that was.
If my memory serves me didn't Danzo say the last he saw of Madara was during the Massacre. Was that Madara or Tobi? Maybe I missed the explanation?