[Tomalak]

I advanced on the right flank, and positioned my soldiers behind a building there (on the right side, in a field), then stayed there occasionally shooting at Germans, until the main part of the penal battalion (AI soldiers) approached the main trench. When they came really close to the MG, I attacked across the road.

What you can do, is hide behind the building, wait until the MG is focused on AI soldiers in the center, then take direct control over one of your soldiers, crawl across the road, get near to the fence, and then open fire at the MG guy while he is turned towards the center. There is also a destroyed vehicle in the middle of the road, providing some cover.

EDIT: If you don't want to wait: there are a couple of enemy soldiers near the building on the right, one of them hidden in the bushes. Be sure to kill at least one of them. Then position your men behind the building, where they are safe. Search the dead German(s) and take his grenades. Crawl with one of your soldiers across the road, get into range and throw a grenade (remember to "cook" it a bit) on the MG killing the soldiers there. Then simply rush to the trenches. Be careful not to go too far to the right when approaching the field, as its mined.