From The Watchismo Times:
Pocket watches were a pain in the ass to fumble around for during battle, something needed to be done to keep soldiers hands on their guns as well as synchronize combat.
"When German Emperor Wilhelm I visited the Berlin Trade Fair and saw some experimental wrist watches made by Girard-Perregaux of La Chaux de Fonds in Switzerland. He gave an order for 1,000 of these for the German Imperial Navy, and as many as 2,000 such wristwatches were delivered in 1880. This began to change in the nineteenth century when watches were first used to co-ordinate military operations. Pocket watches were awkward to use in combat situations; under a great-coat, on horseback, or under fire, and so military men began fitting pocket watches into cups on specially made leather straps, or asking manufacturers to fit them with chains or straps, so that they could be worn on the wrist."Many military watches had a special feature for those "in the shit." A "trench guard," (or "grid" or "grille") covered and protected the dial with medieval-style armor. Those not intended for war were classified as "hunter" cased, often more decorative than protective.