This book explains why Stalin purged the Red Army during the Great Terror of 1937-1938, a decision that gutted the Soviet High Command and led to the execution of a group of its most senior officers, including Marshal Mikhail Tukhachevskii. In examining civil-miitary relations from 1917, this book advances an entirely new explanation of the military purge, showing that Stalin sanctioned this attack on the Red Army not from a position of confidence and strength, but from a position of weakness and misperception.