Then There Were Three (1961)
When an American attack on the German-held town of San Corrado results in the Germans being forced out of the town, they don't have time to take along a top Italian partisan leader they have captured and imprisoned. Fearing that the Americans will turn the man loose to organize more partisan attacks on their forces, the Germans send one of their top agents to infiltrate the town, posing as an American soldier cut off from his unit, and assign him to re-capture the partisan leader and bring him back for interrogation--or, if that's not possible, to kill him.
A Lost Patrol Loving, Fighting and Dying Together - But One is a Nazi Spy!
Continuity
When the one soldier is playing with the German/Austrian bayonet it has a short Quillion or Guard. When it is used later to commit a murder it has a FULL Quillion or Guard. It is NOT the same weapon.
Factual errors
At least three of the men in the makeshift squad are carrying Thompson Sub Machine Guns. While common in Cavalry Recon units or Armor units, these were usually only issued to senior NCO's in the Infantry and/or to the specialists in the weapons squads. Three Infantry stragglers in a group of eight carrying them is unbelievable.
Based upon the line about Salerno, this action takes place in 1944. By 1944 virtually all front-line American Infantry carried the semi-automatic M-1 Garand. The rifles that the men are carrying are the bolt action M-1903A4 Sniper rifle minus scopes. These rifles did not have front sights. These weapons were only issued to select sniper scouts and would NOT have been general issue in an Infantry unit in 1944.
The officer has a metallic bar on his collar and the Sgt. has rudimentary stripes on his sleeve and markings on his helmet front. No experienced WW2 combat leaders would go into a battle so obviously marked and inviting the attention of enemy snipers.
The Lieutenant is carrying an M-1903A4 sniper rifle without a scope or front sights. He would have issued a semi-automatic M-1 Carbine or a Sub-Machine Gun. M-1903A4's were only issued to sniper/scouts, not to officers or regular Infantry.
The troop in the town are still engaged with the Germans just outside the town. They are in a combat zone. Yet nobody hesitates to salute superior officers despite that making them prime targets for enemy snipers.