 Complete the following phrase:  Upon his graduation, Bobruk was appointed a platoon commander with the 18th Saratov Cavalry Courses on 1 August 1921, and in May 1922 he was transferred to Tashkent to hold the same position in the 15th Almaty Cavalry Courses of the Turkestan Front. Between November 1922 and June 1923 he underwent retraining at the Turkestan Front cavalry refresher courses in Tashkent. Upon graduation, he was sent to the 2nd Hisor Cavalry Regiment of the 1st Separate Turkestan Brigade, serving as a platoon commander and assistant squadron commander, regimental reconnaissance officer, and squadron commander. With the regiment, he fought in battles against the 