Explain the significance of the followin line"he has put a knife on the things that held us together and we have fallen apart

Okonkwo's world has fallen apart. Since the white man has come, his family, wealth and power has crumbled within. Now there is no cohesion among the Igbo people. Fighting the missionaries would mean fighting powerful Igbo leaders as well.

“How do you think we can fight when our own brothers have turned against us? The white man is very clever. He came quietly and peaceably with his religion. We were amused at his foolishness and allowed him to stay. Now he has won our brothers, and our clan can no longer act like one. He has a put a knife on the things that held us together and we have fallen apart.”