This Hammer WWII b-movie was originally a stage-play, and with the contained setting and tons of dialog it's apparent..
But Stanley Baker turns in his greatest performance... a one-man show despite being surrounded by character-actors like faithful sergeant Gordon Jackson countered by idealistic reporter Leo McKern and priest Guy Rolfe, driving the central moral-quandary plot-line...
Beginning with their troop of disheveled British soldiers, lost and trudging through the Burmese jungle, happening upon a two-hut village where Baker's no-nonsense captain figures he MUST scare an informer by killing two elderly locals...
The best scenes occur during this first half when Baker's lethal, cold-blooded methods start becoming more clear and, because of the vital information gained, somewhat logical, and he never wavers to the ethical humanity in a village foreshadowing future Vietnam films (and their tropes) about murderous white soldiers...
These include Brian De Palma's CASUALTIES OF WAR and Oliver Stone's Oscar-winning PLATOON, still paling to this low budget, obscure gem mostly thanks to Stanley Baker...
Keeping up the same stubborn, determined intensity when the Japanese, led by an English-speaking, philosophizing Philip Ahn, turns the tables, and the adaptation becomes even more stagey and yet with tight, edgy suspense by Val Guest, one of Hammer's best directors, YESTERDAY'S ENEMY keeps the audience as locked-in as its unflappable leading man.