During my submarining career (1982 - 1987), I watched several movies on the mess deck. Some (Angel of H.E.A.T.) were more enjoyable than others (Wrong is Right).
There was one that kind of mysstified me, though. It could have been filmed in black and white, althiough I can’t swear to that. I found it kind of dry, as far as dialogue and action were concerned.
Some plot elements were that it took place in an unnamed, probably Eastern European country; the conspirators appeared to be the heads of the branches of the military (I’m not sure, but the national police may also have been involved); there seemed to have been some internecine jockeying for status based on how crucial each general’s branch of the military would be to the success of the coup (the Air Force guy seemed to carry the day, IIRC); and at the end of the movie, although the coup was successful, a couple of the generals were betrayed by the junta. They were seated on fancy dining room chairs in the middle of a field, and shot by a firing squad. Another detail that wants to be mentioned is that there was no musical score. (But it wasn’t The Birds :p)
The only movie I remember seeing where men were executed by firing squad while sitting down in chairs was Breaker Morant. But that obviously doesn’t fit the rest.
Sounds like a Canadian made movie, starring Donald Pleasance and Donald Sutherland as the Tank General, who ends up shooting some of his co-conspirators.