It was converted into a signal aircraft warning regiment after the United States entered World War II.

[3] An unrelated 321st Armored Cavalry Regiment briefly existed postwar in Virginia as a reserve unit.

The distinctive unit insignia consisted of a standing grizzly bear holding a garland of oak leaves and acorns tied with a ribbon in his paws over a gold background.

The regimental motto, "Tiens ta Foi" (Hold thy Faith) was attached on a ribbon scroll below the insignia.

The coat of arms was of a similar design except that it omitted the motto and included the Organized Reserve Minuteman crest above the shield.