Stahlhelm, Head Wounds

As the war entered the trench warfare phase, the number of casualties on all sides suffering from severe head wounds (often caused by shrapnel) increased dramatically. The French were the first to see a real need for more effective protection — in late 1915 they began to issue Adrian helmets to their troops. The British and Commonwealth troops followed with the Brodie helmet, which was also later worn by US forces, and the Germans with the Stahlhelm.

Friedrich Shwerd of the Technical Institute of Hanover. In early 1915, Shwerd had carried out a study of head wounds suffered during trench warfare and submitted a recommendation for steel helmets, shortly after which he was ordered to Berlin. Shwerd then undertook the task of designing and producing a suitable helmet.

Source: Wikipedia > Stahlhelm