This may sound like i'm letting my butt do the talking but the reason i say this is because as we all obviously know tsunade is the grandaughter of madara's rival hashirama senju,not only that but she was also 1 of the 5 kage who fought and lost to madara badly and even though her body's messed up in a bad way she's the only one of the 5 kage who seems conscious and able to talk.

SO! basically what i'm trying to say is when we last saw tsunade it was obvious that she and the other kage failed to stop madara and were left for dead and even though tsunade's top half is separated from her bottom half and she looks like she's at death's door she still managed to summon katsuyu and from what she said i'm guessing she plans on at least healing the other kage possibly via katsuyu incase she was to die and even though katsuyu offered to heal her i have a feeling that tsunade feels that maybe it's her time to go meaning she doesn't want to be healed etc.

Furthermore seeing as she knows of what madara is capable of eg multiple clones each in susano'o form,perfect susano'o,his own abilities,hashirama's abilities and the rinnegan and the fact that he seems undefeatable and to make things worse he can't die etc i'm guessing that like jiraiya did when he fought and lost to pain tsunade with the limited time she has left might have relayed a message to katsuyu for naruto and the alliance about madara and had katsuyu tell hq what has happened to her and the rest of the kages and that madara is heading to naruto's battlefield to capture the 9 tails and she also must have warned about madara's abilities and what he's capable of, this could be a possible reason why shikaku formulated a plan with the alliance on how to attack madara, his weakesses etc and also how to deal with obito and the jubi.

P.S This is just a theory.