As he is leaving Benin Home, Ishmael says farewell to his friend Alhaji, who salutes him while whispering, "Goodbye, squad leader." “I couldn't salute him in return,” Ishmael writes (p.180). Why?

At this point in the novel, Ishmael is leaving his soldiering behind forever. He is no longer a squad leader. Alhaji is no longer under his command. To salute would have meant he still clung to their lives as soldiers..... the truth, he would always remember, but he had no desire to hold onto the past.