Um. I've heard of this. I think he is, ahem, SHOWING THE FLAG. Also, either it is very cold and that is snow, or very hot and that is sand. Lastly, from the presence of the second flag, I assume it is an ambush. (Don't go up there, sir! There are Two of them!)
Is he part of the Siberian Expedition of 1919? My grandfather served with it. I don't know much more about his involvement other than that he was there...
This is the staff of the American embasy in Petrograd having fled the city engaged in trying to cross the lines of the White forces on or near the Finnish frontier. The guy with the flag, by his uniform, is probably one of the embassy marine guards. Some one, probably the guy with the other flag one can see, presumably said something like 'Ok private Doberman get up there on the skyline and wave the flag around so we can tell if its safe to procede'. Its a sign of the change in the times that no one caught up in a civil war today would think of standing on the skyline with a big stars and stripes (at least not longer than it takes to thumb the safety catch off a Kalashnikov) but then again today they would all go out by Blackhawk anyway.