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

In 1935, the regiment participated in a 33rd Division staff exercise at Camp Grant, which was planned and supervised by Colonel George C. Marshall, then the senior instructor to the Illinois National Guard.

[3] The 318th usually held its inactive training period meetings at Chicago's Post Office Building.

Its primary ROTC feeder school was the University of Illinois and its designated mobilization training station was Camp Grant.

The distinctive trimming was a vertical representation of the original Flag of Chicago, where the unit was based.