The Twenty-First Corps was activated on December
6th, 1943, at Camp Polk, Louisiana, and was responsible
for training an estimated 200,000 men and 70 different
units of varying sizes before it embarked for the
European Theater in November of 1944.

The shoulder patch worn by the XXI Corps was approved by
the OMG on April 3rd, 1944. The crossed arrows represent
the fighting power of the Corps, and the acorn is a symbol
of strength while the four-leaf clover is a sign for good
fortune. The blue and white portions of the insignia suggest
the colors of the Corps' distinguishing flag.