he graduated from the Vystrel commanders' improvement courses. Koroteyev was appointed chief of staff of the 14th Rifle Regiment in January 1934 before becoming regimental commander in March 1935. He was appointed chief of staff of the 27th Rifle Division, part of the Belorussian Military District's 4th Rifle Corps, in July 1937, and became division commander in February 1938. In the same year, he joined the Communist Party of the Soviet Union. Koroteyev led the 27th Division in the Soviet invasion of Poland in September 1939, during which it advanced into Polish territory annexed to the Soviet Union as western Belorussia. During the Winter War he was a division commander. Koroteyev commanded the left-flank group of the 15th Army of the North-Western Front and led the fighting on the mastery of the islands, Petäjäsaari and Maksimansaari in Lake Ladoga. In March 1940, he was appointed inspector of the infantry of the Leningrad Military District before taking command of the Kiev Special Military District's 55th Rifle Corps in March 1941, which he commanded at the beginning of Operation Barbarossa, the German invasion of the Soviet Union, on 22 June. World War II The rout of the 37th Army From the beginning of the invasion, Koroteyev led the corps in the border battles as part of the Southwestern Front. In July, it fought in fierce fighting in defense of the Dniester line as part of the Southern Front's 18th Army, but was forced to retreat beyond the Southern Bug by Axis troops. In August the corps was disbanded, and he was made deputy commander of the 18th Army for the rear. Southern Front In October 1941 he was appointed commander of the front's 12th Army, after it failed to hold Dnepropetrovsk and the defensive line on the Dnieper. Koroteyev led the army in the battles in the Donbass region and Rostov defensive operation. The compounds of the enemy army has suffered heavy losses, but under the pressure numerically superior enemy Donbass had to leave. Successfully operated commander in his first major offensive near Rostov in November - December 1941. He led it in the defense of Rostov and a counteroffensive against German troops during the Battle of Rostov. In March 1942, Koroteyev was made assistant commander of the Southern Font. In August, he took command of the 11th Guards Rifle Corps, part of the Transcaucasian Front's 9th Army, leading it in the