numerous fortifications, particularly the Kakhovka Platzdarm, and held senior positions at the headquarters of the North Caucasus Military District. In 1920, he was chief engineer of the Soviet 5th Army and the assistant of chief engineer of the Southern Front (second formation). Karbyshev supervised engineering support for the assaults on Chongar fortifications and Perekop against the White movement in the Crimea. Interbellum period in academy From 1923 to 1926, Karbyshev was the Chairman of the Engineering Committee of the Main Military Engineering Administration of the Red Army. In 1926, he became an instructor at the M. V. Frunze Military Academy, and in 1936, he joined the General Staff Academy. In 1929, Karbyshev was appointed to design Stalin line and Molotov line. In February 1934, he was appointed the Head of Department of Military-Engineering Science of General Staff Academy. Since 1936, Karbyshev was an assistant to the Head of Department of Large Formations' Tactics of the Academy. He was promoted to Professor in 1938, and to the military rank of lieutenant general in the Corps of Engineers in 1940. In 1941, Karbyshev was awarded doctorate in military sciences. He published over 100 research papers in military engineering and military history. He specialized in the construction and demolition of obstacles, and in the issues involved in crossing rivers and other water obstacles. His articles and manuals on the theory of engineering and battlefield operations and tactics were mandatory for reading by Red Army commanders in the pre-war years. He also served as a consultant for the restoration of the Trinity Lavra of St. Sergius outside of Moscow. World War II During the Winter War of 1939–40 between the Soviet Union and Finland, as a member of the group to the assistant of chief of the Main Military-Engineering Administration in fortification construction Karbyshev travelled to the front lines to advise troops on engineering support in breaching the Mannerheim Line. In early June 1941, Karbyshev was sent on the inspection trip to Western Special Military District. The German invasion occurred while he was at the headquarters of Soviet 3rd Army in Grodno. Two days later, he moved to the headquarters of the Soviet 10th Army. On June 27, 1941, the army became surrounded and eventually destroyed during the Battle of Białystok–Minsk. In August 1941, Karbyshev suffered from post-concussion syndrome in combat at the Dnieper River in what is now the Shklow Raion, Mogilev Region,