sentences:  During World War I, Dean was commissioned a Major in the Ordnance Corps, and worked on development of armor, especially of helmets.His work guided and informed helmet development in the US, and possibly in other countries, at least until the 1980s, although his preferred design was rejected in 1918 and c. 1937, as its resemblance to the German Stahlhelm was considered too close.He was the author of "Helmets and Body Armor in Modern Warfare".