Insignia Description
A Gold color metal and enamel device 1 5/32 inches (2.94 cm) in height consisting of a shield blazoned: Azure a polar bear statant on an ice cake Argent: on a canton Or a fess Sable between three martlets of the like two and one. Attached below and to the sides a Gold scroll inscribed “III T bl K b Pb III A E T b” in Blue letters.

Symbolism
The polar bear on its blue background is copied from the unofficial shoulder patch of the North Russian Expeditionary Force, of which this Regiment was a part during the years 1918-1919. The Regiment, organized in 1917, was made up to a large extent of men from Detroit, and was known locally as “Detroit’s Own.” The canton bears a part of the coat of arms of Cadillac, the founder of Detroit, and is symbolic of the origin of the Regiment and of its 1924 allocation. The motto is pronounced as though spelled in English “shtuk ryshayet.” Literally translated it is the “The Bayonet Decides,” freely translated it may be rendered “We Finish With The Bayonet.”

History
The distinctive unit insignia was originally approved for the 339th Infantry Regiment on 9 June 1924. It was redesignated for the 339th Regiment and amended to include the motto on 5 August 1960.

Source: The US Army Institute of Heraldry