The aircraft carrier deck crew wore N-1 deck jackets during World War II and the Korean War. The thick cotton shell and alpaca or wool lining gave the deck crew the needed warmth and protection from the elements during extreme cold weather conditions. US Navy produced the initial series in Navy blue to symbolize the Navy before changing to Khaki.
The US Navy developed three “N” systems. In addition to the cold climate N-1, the N-2 system for rainy and the N-3 system for tropical conditions. Despite these climate divisions, old photographs indicate sailors rarely used these systems according to regulations, opting instead to mix and match to suit their layering need and preferences.