How does Okonkwo know that Umuofia would not go to war?

Okonkwo knows that Umofia will not risk war against the powerful white men so he takes matters into his own hands.

Okonkwo senses that the tribe will not go to war. He knows this because he can hear voices from his clan asking: “Why did he do it?” Okonkwo leaves. It can be argued that Okonkwo's murder of the court messenger is both an act of fate and an act of free will.