The two field artillery regiments were demobilized at Camp Kearny, California, on 22 December preceded by the trench mortar battery on the previous day.

In July of that year, the regiment conducted its annual summer training with the 52d Cavalry Brigade at Mount Gretna.

Its designated mobilization training station was the York Concentration Area in Pennsylvania, and its primary ROTC feeder school was the Valley Forge Military Academy.

[5] After the Pearl Harbor resulted in the American entry into World War II, it was converted into the 66th Tank Destroyer Battalion on 30 January 1942.

The regiment's coat of arms was similar to the distinctive unit insignia except that it added the Organized Reserve crest, a Minuteman, and omitted the motto.