Chaplain Tappman may be the most decent character in the novel. He is consistently a friend to Yossarian; the first line of the novel indicates that Yossarian immediately cares a great deal for the chaplain as well. The chaplain grows from a timid, ineffectual fool to a bold and assertive force for reason and justice as the novel progresses. Throughout, he is kind and introspective.
If Tappman ever were going to fold, it would be during his interrogation. Up to then, we have found him to be a very timid man, easily intimidated, frightened of loud voices and aggressive types. Even Tappman's assistant, Corporal Whitcomb, bullies him. He frequently points out the chaplain's "faults" (according to Whitcomb) and has Tappman on the defensive, apologizing rather than directing his assistant. Despite all this, we have seen that the chaplain has courage. He wants to do the right thing and attempts to speak to his superiors, such as Colonel Cathcart, about legitimate grievances from the men. But the interrogation in the cellar (Chapter 36) plays into all the chaplain's insecurities.
Instead of caving in, the chaplain becomes stronger and more assertive under pressure. He is whisked off to the cellar with no explanation of the charges against him, controlled by frightening figures whom he cannot identify. There, the chaplain is subjected to a harsh and arbitrary inquisition about matters that seem insignificant: a letter forged by Yossarian, a plum tomato given to Tappman by Cathcart. The chaplain has no representation and no chance. When he tries to defend himself, he is accused of lying. In the end, he is found guilty simply because he was accused. Although the captors release him, Tappman is warned that he will be "under surveillance twenty-four hours a day." Still, the first thing he does upon his release is to challenge Colonel Korn about the deaths of the twelve men, including Nately, on the mission over La Spezia that morning. Later, as he is saying goodbye to Yossarian just before the protagonist flees from the hospital, the chaplain reveals that he is a new man. He volunteers to remain behind and make life miserable for the authorities: "I'll persevere. I'll nag and badger Colonel Cathcart and Colonel Korn every time I see them. I'm not afraid." He is even ready to take on his assistant, Whitcomb. Chaplain Tappman has become a fighter.