'Birken-Bewegung' was the German retirement within 'Birke' of Generaloberst Dr Lothar Rendulic’s 20^th Gebirgsarmee first to the 'Sohjana-Stellung' on the Sohjana river in northern Finland, and then from 15 September to the 'Kuusamo-Stellung' farther to the north-west in the same country (6 September 1944/25 October 1944).