"Horse-Mechanized Cavalry" - From August 9, 1921 through November 16, 1940, the 102nd Cavalry had been a unit of the 21st Cavalry Division. In November of 1940, after two years of experimenting in a search for a highly mobile ground reconnaissance force, the War Department selected seven National Guards and two Regular Army Cavalry Regiments to be reorganized as "Horse-Mechanized Cavalry". With a new National Emergency in sight, and mobilization already  under way, the "Essex Troop" was honored to be one of those selected. So it was that on 16 November 1940, the 102nd was reorganized as the 102nd Cavalry Horse/Mechanized and relieved from assignment to the 21st Cavalry Division. It was from the 102nd Cavalry Regiment that the 117th would later be created.