So this is the battle between Vali and Sugriv from Indian epic Ramayana. The whole fight between Vali and Sugriv happened because of a misunderstanding. Surprisingly the world was, is and will be the same. People still fighting because of minor and major misunderstanding.
The epic says (this is from Wikipedia though )
Vali had been too outraged to heed his brother Sugriva after he had sealed the entrance to a cave in which Vali was fighting a rakshasa named Mayavi. Sugriva had mistaken the blood flowing out of the cave to be his brother’s, blocked the entrance to the cave with a boulder and left for Kishkindha, assuming that his brother was dead. When Vali had emerged victorious over the rakshasa, he had found that the entrance to the cave was blocked. He journeyed back to kingdom to find Sugriva ruling in his place. Sugriva tried to explain the situation to Vali, but Vali, enraged, would not listen.
This was the root cause of the fight. So here comes our Vali, all charged up for the war.