The crew of a 15-cm Kanone 18 taking it easy during training. They belong to the heavy artillery battery of Artillerie-Regiment 132, which in turn is part of 132. Infanterie-Division. Like so many other divisions in Army Group North, it was trapped in the Courland pocket and surrendered to the Red Army in March, 1945.
Artillery was (and is) an important part of warfare, but the Germans often suffered from ammunition shortages. They had to be conservative with grenades, and fire them off in short, concentrated barrages. The Red Army could amass huge numbers of field guns and howitzers, and let loose massive barrages. The US Army was proficient in concentrating artillery fire in such a way that all grenades arrived at the same time (“time on target”), and seldom had any real ammunition shortages. As in so many other cases, it is a mystery how the Germans could hold out for so long, considering the shortages of just about everything.