"A Quality of Mercy" is the fifteenth episode of the third season of The Twilight Zone, and was first broadcast in December of 1961. It starred Dean Stockwell as Lt. Katell, and Albert Salmi as Sgt. Causarano. It also had a role for Leonard Nimoy, although it was not a prominent role. Since this episode takes place in The Philippines during World War II, which is where Rod Serling served in the military, it could be based in part on Serling's actual experiences.
The episode takes place on August 6, 1945, in The Philippines, where a platoon of tired soldiers are engaged in the last phase of mopping up operations. The infantryman are acting as observers for a mortar platoon that is shelling a cave with holed-up Japanese soldiers, and see no reason to directly attack the cave. However, when a eager young lieutenant takes over their platoon, they may be forced to kill and die. Unless, of course, the lieutenant undergoes some type of eerie, unexplainable experience that makes him reconsider the rationale of war.
This episode continues a theme in the third season of The Twilight Zone, where there is many stories focusing on war, often with the fantastic element only used to address real issues of armed conflict. Unlike the first season's "The Purple Testament", which depicted a positive example of military culture, this episode focuses on the idea of the officer corps as being martinets. Whether this was purposely a social comment on military hierarchy, or just an expedient for the episode's dramatic structure, is something that (as with so much of The Twilight Zone) it is difficult to tell. And as with many other episodes in the third season that seem to comment on the outcomes of war ("The Shelter", "The Mirror", "The Passers-By", even possibly "The Midnight Sun"), it is hard to tell whether Serling's more direct statements are the result of more artistic freedom with the established popularity of the show, or whether his own anti-war views were beginning to grow.