We learn that Clevinger is a Harvard graduate who is academically very bright but has little courage. He and Yossarian trained together in cadet school in Santa Ana, California.
Lieutenant Scheisskopf is obsessed with winning parade competitions every weekend for worthless pennants as prizes.
He appoints his own officers instead of letting the men elect them, much to Clevinger's indignation.
Scheisskopf is so busy preparing for the parades that he doesn't notice that his wife is cheating on him with any and every man who wants her. This includes Yossarian, who sleeps with her every week, even though he's in love with one of her friends, Doris Duz. Yossarian is in love with her, but Doris does not return his love, so Yossarian takes his frustration out on Mrs. Scheisskopf by having sex with her.
Clevinger, against Yossarian's advice, suggests that Scheisskopf let his men elect their own officers. Scheisskopf takes Clevinger's recommendation and miraculously starts winning all the parades.
Then Scheisskopf promptly accuses Clevinger of conspiracy to overthrow the officers that Scheisskopf appointed. Clevinger is brought before the Action Board for an inquisition. The Action Board is dominated by a totally irrational and bloated colonel who constantly threatens to tear Clevinger (and his fellow Action Board fellows) limb from limb.
The inquisition often makes Clevinger say contradictory things (which are all perfectly fine by the Board) and they sentence him to fifty-seven tours as punishment.
Clevinger is not as dismayed by the actual sentence so much as by the hatred he saw in the Board's eyes – hatred for him from his own countrymen.