Inspired by the fishtail parka that was used for the first time in 1951 by the United States Army during the Korean War. This is where the jacket first got it's model name M1951 or M51 (M standing for 'military' and the year when it was standardized).  The soldiers were equipped with the parka to cope with extreme weather conditions while in combat. 

England in the 1960's, the fishtail parka became cultural wardrobe icon with Mods as it was quickly adopted by them for it's statement of originality and style.