In the movie saving private ryan there is a scene in the film where capt miller and his squad are going through the town of Nueville. One of the paratroopers sends a runner to hook up with a captain on the other side of town. The runner or measenger gets shot. Even though the runner was down the Germans still fired at him. Capt miller states,"as long his lungs have breath in them he still carries the message we do the same thing." Is this true??
Probably. There is an interesting book, two actually, the first is called Retribution: the battle for Japan 1944-45, the second is called Armageddon: The battle for Germany 1944-45. he has another history called Inferno: the world at war 1939-1945. The first two are all you need to read.
They are authored by Max Hastings a highly regarded British historian. His works are remarkably readable and he pulls no punches. He does not sugar coat what we or our enemies did. Speaking with first hand sources he documents many instances where German prisoners or wounded German or Japanese soldiers were shot.
A book called Yankee Samurai about the Niesi soldiers, the Japanese Americans. In the book it claims that the no quarter war in the pacific began when US Marine Raiders attacked the Gilbert Islands (before Tarawa) and killed all the Japanese garrison on one small island. Some marines were accidentally left behind and were executed by the Japanese. This started a tit for tat in the Pacific. This probably no true since the Japs had a reputation of brutalizing prisoners since it was against their credo to surrender, they had no regard for those who did.
In Germany it was a bit different. They had the same ethical code of honor to a point that the Brits and Americans did. No so the Russians since the Soviets were not signatories to the Geneva Convention the Germans did not feel they were obligated to offer them protection afforded those who did sign it. So Russians were abused and killed out of hand.
Tactically it was common for prisoners to be killed in some circumstances. For instance paratroopers did not have the means to hold prisoners and did not want to turn them loose so most were shot. Band of Brothers documents that.
Another case was Germans fighting up to the last second then just about the time they knew they were going to get killed, throw down their weapons and try to surrender. Well if our troops blood was up, they would just shoot them. Imagine yourself in that situation, this guys has just shot your best friend and you have the drop on him and he goes, "Oh, I want to surrender now!" I am sure you and would I would say,"Sorry too late!" Boom. Recall the scene in Saving Private Ryan when the Germans come out of a beach bunker with their hands up after mowing down Rangers yelling "Nicht Scheissen! Kamerad! Kamerad!" Two rangers shoot them and one says to the other "What was he saying, what'd he say?" The other laughs and says referring to the guys raised hands: "Look I washed my hands for supper!"
So yes a runner would be shot pretty much on sight. In absence of effective radios, runners were the only way orders could be conveyed from command to sub units or from unit to unit.
When you have read enough history you will come to realize that communication breaks down at the first gunshot. Lack of good communication has been the norm rather than the exception and is the cause of most military disasters.