In World War II, some U.S. Navy sailors wore unusually large helmets with a unique purpose. Here's the history behind this ...

After the war, the U.S. military began to standardize Aircrew Flight Equipment (AFE), leading to the development of helmets tailored to specific operational needs, climates, and oxygen systems.

Brass spikes & horsehair plumes : a study of U.S. Army dress helmets, 1872-1903 / by Gordon Chappell Smithsonian Libraries and Archives ...