They went to war because Caesar wanted more power. Caesar won because he had more men and he was already powerful in the beginning. "But indeed, sir, we make holiday to see/ Caesar and to rejoice his triumph"(I:i:Ln 31-33). Pompey thought he would have enough men to defeat Caesar because Caesar is very gulliable and believes everything anybody tells him.
Act 4 Scene 2
Calpurnia has a dream telling Caesar he is going to die. Caesar tells Decius "She dreamt tonight she saw my statue,/Which, like a fountain with a hundred spouts,/ Did run pure blood, and many lusty Romans/ Came smiling and did bathe their hands in it"(II:ii:Ln 76-79). Decius tells Caesar " This dream is all miss interpreted;/ It was a vision fair and fortunate:/ Your statue spouting blood in many pipes,/ In which so many smiling Romans bathed¨ (II:ii: Ln 83-86).
Act 5 Scene
Caesar is walking to work and he sees the Soothsayer and says "The Ides of March are come"(III:i:Ln 1). The Soothsayer tells Caesar "Ay,Caesar, but not gone"(III:i:Ln 2). Which is indicating that the day is not over and anything could happen, but Caesar does not believe him and keeps walking. Caesar then realizes everything everyone told him was true and the dream that Calpurnia had was actually going to happen. He has his head in a daze and is believing what he wants to, and in the end Caesar dies.