During Stalins Great Purge in the late-1930s, which had not ended by the time of the German invasion on 22 June 1941, much of the officer corps of the Red Army was executed or imprisoned and their replacements, appointed by Stalin for political reasons, often lacked military competence. Of the five Marshal of the Soviet Union appointed in 1935, only Kliment Voroshilov and Semyon Budyonny survived Stalins purge. Tukhachevsky was killed in 1937. Fifteen of 16 army commanders, 50 of the 57 corps commanders, 154 of the 186 divisional commanders, and 401 of 456 colonels were killed, and many other officers were dismissed. In total, about 30,000 Red Army personnel were executed. Stalin further underscored his control by reasserting the role of political commissars at the divisional level and below to oversee the political loyalty of the army to the regime. The commissars held a position equal to that of the commander of the unit they were overseeing. But in spite of efforts to ensure the political subservience of the armed forces, in the wake of Red Armys poor performance Soviet invasion of Poland and in the Winter War, about 80 percent of the officers dismissed during the Great Purge were reinstated by 1941. Also, between January 1939 and May 1941, 161 new divisions were activated. Therefore, although about 75 percent of all the officers had been in their position for less than one year at the start of the German invasion of 1941, many of the short tenures can be attributed not only to the purge, but also to the rapid increase in creation of military units.
Question: How many officer groups saw over half of their soldiers killed?
Answer: 4