The "R-1"s were assigned to the cavalry brigades, two platoons of two or three tankettes apiece. All eighteen belonging to the Cavalry Corps were grouped into the ad hoc "Korne Mechanized Detachment" during the opening stages of Operation Barbarossa, but all were out of commission by 1 October. Twenty-nine of the original thirty-five were allocated to the six cavalry divisions (redesignated from brigades on 25 March 1942) that successfully participated in the German 1942 summer offensive, codenamed Case Blue. The four "R-1"s belonging to the 1st Cavalry Division's 1st Mechanized Squadron had to be set on fire as no fuel was available for them when the division was encircled outside of Stalingrad in November 1942 as part of the Soviet Operation Uranus counter-offensive. The 5th and 8th Cavalry Divisions had lost at least five "R-1"s during the same time trying to solidify the crumbling Axis defenses after the Soviet breakthroughs. Both divisions supported the Germans as they attempted to relieve the Stalingrad Pocket in Operation Winter Storm, but were shattered when the Soviets counter-attacked the unsuccessful relief effort in late December 1942. Two other cavalry divisions remained in the Kuban bridgehead after the German withdrawal from the Caucasus, but their two remaining serviceable "R-1"s were withdrawn back to Romania during the spring of 1943 as obsolete. On 30 August 1943 only thirteen "R-1"s were available, all assigned to the Cavalry Training Center, although this increased by one on inventories dated 25 March and 19 July 1944. Nothing is known of any action involving "R-1"s during 1944, but eleven reinforced the 2nd Armored Regiment in Czechoslovakia when it reached the front on 26 March 1945. By 24 April the regiment only had one R-1 available, but none were reported as available after that date.