Season four opened with a two-part premiere that aired on 12 September, 1975. Written by series developer Larry Gelbart as well as James Fritzell and Everett Greenbaum.

To deal with Trapper’s (Wayne Rogers) abrupt departure from the series, as well as Blake’s (McLean Stevenson) leaving for home, the episode had to reintroduce the series (again) while welcoming regular viewers back to the 4077th, it also adds Jamie Farr to the opening credits. Hawkeye (Alan Alda) arrives back from an R&R to find Frank (Larry Linville) and Margaret (Loretta Swit) still trying their best to instil some Army decorum in the camp, and Radar (Gary Bughoff) delivers the news that Trapper is on his way home – discharged and Hawk has missed him by only a couple of hours.

There’s a new doctor B.J. Hunnicutt (Mike Farrell) to be picked up and if Hawkeye races time, in an appropriated jeep and passenger (Radar) he may make it in time to say goodbye to his friend. Who he says he’s been living with for a year – suggesting that the first three seasons all took place in the space of a year.

Upon arriving at the airfield, Hawk learns he’s missed Trapper by an ten minutes, and while Radar collects Hunnicutt, their jeep is stolen. Consequently the trio go for a drink, Hawk gives B.J. a crash course on the 4077th and the war, while Radar frets over the jeep.

Stealing a jeep, they head out preparing to introduce B.J. to the Swamp, the 4077th and its inhabitants.

Part 2 aired the same night and shared the same writers. The episode continues the story of B.J.’s arrival in Korea, and as the trio travel to the 4077th, they come across a family using their daughters to test a grazing field for mines, get a flat tire, come under attack, and find themselves tending to wounded during a shell attack on an Army patrol.

The episode balances the humour and drama, and shows B.J. very quickly how horrific the war is, and allows him to form a fast friendship with Hawk and Radar.

In fact, they all stop, just outside of camp, to visit Rosie’s Bar to tie one on before heading in to report to Frank.

It’s an enjoyable episode, and ends with a roll call of the cast members, who according to the voice over are permanently assigned to the 4077th. And as the roll call ends, we are introduced, ever so briefly to the camp’s new commanding officer, Colonel Henry Potter (Harry Morgan) who arrives just in time for the credits.

So while we’ve said goodbye to some dear friends, the show prepares to carry on, and since it’s boasting a solid cast, as well as a great writing team, the series seems to be in good hands, and we, like Hawkeye are ready to welcome the new viewers that tuned in to see how the new cast members would work with a company that has already served three years together.

I remember seeing Part 1 as a child, because I know it bothered me that Hawkeye didn’t get to say goodbye to Trapper (being an Air Force brat you are totally used to this concept, but that doesn’t make it hurt any less).

Chain of Command, which sees Potter’s first full episode, was written by Fritzell and Greenbaum and debuted on 19 September, 1975.

Hawkeye is troubled to learn that the new commanding officer, Potter, is regular Army, and is afraid he’s going to be a promoted version of Frank (who goes temporarily AWOL when he learns he’s not staying in command). According to Potter’s record, he’s served since The Great War, and hasn’t been in surgery for a couple of years.

Potter calls all his officers in, to get to know them, lay down the regulations and assert his command. However, after one day and night of meatball surgery and seeing how good the unit works together, he relaxes a little, when he reveals he could use a drink.

Potter, Hawkeye and B.J. forge a quick friendship, and the colonel begins to accept the eccentricities of the camp, while working to understand and lead those under his command.

Potter is different from Blake, and Morgan makes him a completely realised character from the off. Bringing he and Farrell in at the beginning of the fourth season must have been tough, but both actors are up to the challenge, and ease themselves into the ensemble, freshening it up a touch,while the show carries on delivering his laughs and drama.

More next week!