Cast changes after the pilot

In addition to staff changes, the cast also changed between the pilot and the series. The Beecham character (played by Harry Dean Stanton) was dropped and, over the objections of Robert Pirosh, the name of the Cajun soldier was changed from Caddy to Caje. Pierre Jalbert says, “Caje was a contraction of Cajun. I think it was Vic that started to call me that and it stuck. I don’t remember if there was any specific reason for it, it just organically took place.”

Combat! went on the air with five regular cast members, three of whom would return for the following season. All the actors who eventually became regular cast members appeared in the first season.

Rick Jason's character of Hanley was promoted from Sergeant to Lieutenant, shattering Pirosh's concept of a show revolving around a small core of enlisted men. This change was made at the suggestion of Robert Altman, whose background as a flyer in the Air Corps may have made it difficult for him to imagine a war fought without officers. Rick Jason adjusted his portrayal from the devil-may-care skirt-chaser, to the cool, calm, and collected officer. The change in rank also put a professional distance between the characters of Hanley and Saunders, dampening the budding friendship established in the pilot. Hanley still retained the sophisticated good looks, bright smile, and easy-going manner — and the hard steel behind the smile.

Vic Morrow had hoped Combat! was his chance to break out of his bad-guy image and change the direction of his career, but he was disenchanted with the pilot. Blees quickly set up a meeting with Vic Morrow. “I admired his work for years and thought he'd be critical to the show's success. It was apparent Vic had very strong ideas, which was fine with me. I respected that. That didn't mean I had to accept the ideas. Rick's stature was far above Vic's. Rick got more money the first year, he had the stature. On a scale of one to ten, I’d say he was about a number seven star.”

Blees’ first meeting with Vic lasted two hours. Vic wanted to walk away from the show after the pilot. “He thought it would ruin his career.” Far from it, Sgt. Saunders became the defining role of Morrow’s career. Morrow created a memorable character in Saunders, the everyman soldier. His powerful portrayal of this tough-as-nails leader far surpassed the simplistic press kit description of him as "strong but sympathetic." Morrow's Saunders was a man of few words, with a fierce loyalty to his men and to his lieutenant.

Pierre Jalbert was pleased to step out of the editing room to play the newly christened character Paul “Caje” LeMay. His character usually acted as the platoon's French translator, letting him script his own French dialogue. Gregarious and friendly, Caje’s character goes through a series of epiphanies as the war tries to crush his spirit. Jalbert's superb performances hardly seems like the work of a newcomer. He creates some riveting moments in the pilot episode as he mourns the loss of his friend and deserts his squad under fire. He ends the season with an equally strong performance in"No Trumpets, No Drums" as he comes to terms with his accidental killing of a French civilian. In an interview for The Squad, Jalbert said, “The first three months were a little scary for me, being in front of that black box. But, I had a great advantage to know all of the technicians who were working on Combat! I had great support from them. After about a year I was very confident. Vic Morrow helped me also by teaching me about screen presence and timing.”

Shecky Greene continued his nightclub engagements while filming Combat! Production often was arranged around his Vegas schedule so he wouldn't have to give up any performances on the strip, for which he was receiving $150,000 per week. The directors would try to shoot his scenes on Mondays and Tuesdays, finishing in time for him to return to Vegas for the Tuesday evening show.

Blees says, “This was typical of the dedication of the guys working there. Greene would work his bit in Vegas. After Sunday’s show, he'd get in an ambulance, sleep on his way to L.A., where he kept an apartment, and get ready for filming the show. We all appreciated that dedication.” Such arrangements weren't possible, though, when Greene was featured in the episode, such as in "The Prisoner" and "The Chateau."

Shecky Greene only appeared in eight episodes. The end came while filming, in 110-degree heat, the final scene for the episode "Far From the Brave." The many re-takes of the scene on Eucy Road (an often-filmed road on the MGM backlot lined with Eucalyptus trees) was the last straw for Greene. He had little patience for method acting and preferred the larger paychecks of Vegas.

Greene discussed his departure from Combat! during an interview on the Charles Grodin show. “I threw everything down and ran. I said that's the end of it. I went to Selig Seligman, the producer, and I said ‘Selig, I quit.’ He said, ‘You can't quit 'cause the whole show's around you and I'm going to get you your own show with ABC.’ ABC was nothing at the time, it was just AB, it didn't even have the C. And, I said I really don't want television 'cause this is not for me, I'm not making direct contact. Not even with the director. [. . .] Uh, and that smell of eucalyptus. How many times can your nose clear up?” Though Seligman wanted Greene to stay, his character wasn't working with the new, darker concept for the show.

Steven Rogers portrayed Doc as a gentle, sensitive youth who is profoundly affected by his battlefield experiences. His character was the only one of the regulars to escape the show unharmed. Steven Rogers' Doc appeared in 21 episodes without a single injury. His mortal blow came not from the Germans, but from the front office. Rogers' work and attitude didn't please the producers and he was released before the end of the first season. According to some on the set, he had expected to be noticed in his Combat! role and that he was going to be the star. “He thought he was going places but nothing really happened. He’s a good looking kid and I can see how he might have bought into that for himself.” Blees says that Seligman fired Steve Rogers because of a negative comment his wife made about Seligman at a party.