In Episode 3 of "SAS: Rogue Heroes", L Detachment attack some Axis airfields in North Africa. The stated intent of the mission is to sabotage planes, trucks, etc., with explosives.
During this mission, the (fictionalised) Paddy Mayne and others gun down apparently unarmed (and moderately drunk) German and Italian airmen and engineers in their mess hall. They're enemy combatants in an active war zone, so on one hand it would seem justified. But on the other hand, they're unarmed, and were given no opportunity to surrender.
Note: I'm putting aside questions of whether it really happened as depicted. That's a question for Movies & TV Stack Exchange.
My question is this: under the laws of warfare in effect at the time (i.e. the North Africa campaign of WW2) were these actions legal, or would they count as a war crime?