This is one of the most poignant, moving episodes of the series. McLean Stevenson was the first of the original TV cast to strike out on his own and leave the camp. (Wayne Rogers also split after this episode, but his departure was not so planned.)
In season 1, ep 24 ("Showtime"), Henry's wife has a son - one he never gets to see, since he never makes it home. While the writers never mentioned the little boy again, that fact alone would make me cry. But Henry's plans to go dancing with his wife and a teary Radar watching the helicopter leave for the last time are some of the most heart-wrenching parts of this show - I cry because I know how it ends, and I cry for the family that waited for a loved one and instead got a messenger. This particular twist was a VERY risky move for the show's producers and writers, and the last scene of this episode was kept under wraps as much as possible.
Watching the show, it is just impossible not to smile when Henry gets his orders, and when he talks to his wife on the phone, even though we all know what is up ahead. Walter Burghoff did an exceptional bit of acting in this episode, but everyone did well in this farewell to their lovable CO. While Harry Morgan was exceptional actor, and Sherman Potter became as close to the group as Henry did, the was no replacement to Henry Blake. Abyssinia, Henry.