On the left. The empty mortar bomb tubes are against the wall, seen between the mortarmen. The right hand mortarman has a bomb in his left hand, ready to reload, more bombs in tubes next to him on the ground. Bomb on the ground behind left hand mortarman probably dud propellent.
On the right. The mortarmen on the right are also ready with the next bomb.

All the large tubes should be large calibre artillery tubes, for the charges.

That mortar tube elevation looks like the bombs will be falling close. Arming distance for the bombs should be at least 40m so the wall isn't a problem. I believe they will know what to do.