The Republic of Estonia declared neutrality in the war but fell under the Soviet sphere of influence due to the Molotov–Ribbentrop Pact and was occupied by the Soviet Union in 1940. Mass political arrests, deportations, and executions followed. In the Summer War during the German Operation Barbarossa in 1941, the pro-independence Forest Brothers captured South Estonia from the NKVD and the 8th Army before the arrival of the German 18th Army. At the same time, Soviet paramilitary destruction battalions carried out punitive operations, including looting and killing, based on the tactics of scorched earth proclaimed by Joseph Stalin. Estonia was occupied by Germany and incorporated into Reichskommissariat Ostland.