In mid-1920, at the peak of the Polish–Soviet War, the regiment was attached to the 8th Cavalry Brigade, which in the area of Ostrołęka opposed Soviet Cavalry Corps of Hayk Bzhishkyan. The 108th Uhlan Regiment set on its first patrol on July 20, 1920, fighting against the advancing enemy in Nowogród. On August 5, it was sent to recapture Łomża, but its 2nd Squadron was surrounded by the Soviets near the village of Kuleszka: two officers and 50 uhlans were KIA.