Interesting.
Before konoha , every clan was fighting for the love of their clan.
Hashi and Madara met when they were both looking for a way to change this shinobi world , they understood each other and became friends with the same goal without realizing they were born as ennemies .
Later , they will make an alliance between clans of the same region , called "village of that country".
With time , something grew between clans of those villages , love between comrades , village unity , the will of fire for Konoha.
Every region of the world does the same , and now villages are fighting for the love of their own village.
Hashimara and Madara understood that making villages is an incomplete way to achieve peace .
They need world unity.How?
Madara's answer is to create an insane ennemy of humanity , to make shinobis unify against that ennemy.
Hashirama thinks there must be another answer and Madara leaved Konoha
When Madara came back to take Hashirama DNA to summon Juubi , Hashimara kicked Madara's ass with a few thousands of spanks , but had no answers , let's try madara's? .
Hashirama planned to give his life to make Madara able to summon Juubi to use it as an ennemy of humanity ( Madara's plan after leaving Konoha) , to make the world unify against that beast , to make everybody a comrade you love , unity of shinobis , a world of peace.
I would say well played guys.
That would explain why Madara is enjoying all the alliance of shinobis jutsus :"Hmmmm , well played ""oooh , it's a strong clan""nice combi , guys" , like he would be at a friendly football match.Obito is more " **** , shit , grrrr , tssssk " like he would be at the world cup final.