I attacked from the right, where there is a slight slope I believe. Enemies struggled to engage me and I was picking them off, I used 2 riflemen to cover me as well so if they did get close we killed them.
As for killing the people on the other side, move down and use the mortars to bombard their side, this should get rid of all their troops over there, or at least enough that the sniper can then pick off the final few
Just be careful as I think there is a barrel which can be knocked over, trapping you in the small section with the 2 mortars, when this happened to me I had a guy hide behind the sandbag bunker thing and in the counterattack he was really useful for throwing grenades and picking off advancing enemies.