On 22 June 1941, the German Army unleashed a devastating surprise attack on the Soviet Union. This attack heavily damaged the Red Army and ultimately shook the foundations of the Soviet state. The June disaster was, in part, the product of a Soviet strategic intelligence failure. In early September 1941, Guderian's Second Panzer Group turned abruptly southward from Smolensk, thrust by surprise into the rear of the Soviet Southwestern Front defending Kiev, and swallowed up over 600,000 Soviet troops. The September catastrophe was due in part to faulty Soviet intelligence. In October 1941 German armies launched their expected thrust on Moscow through sectors the Soviet had not expected them to use. The intelligence failure proved fatal for four Soviet armies and almost led to a loss of the capital. On 17 May 1942 German armies crushed a Soviet attacking force in the Khar'kov region of southern Russia, encircling and capturing over 250,000 men as a prelude to the surprise German strategic thrust that culminated at Stalingrad. Again Soviet intelligence failures played a major role. This document describes this operation.