When the German 18th Army crossed the Estonian border on July 7, 1941, as part of Operation Barbarossa, it was welcomed by approximately 1,125,000 Estonians as liberators from Bolshevism. During the advance through the roughly 47,500 square kilometer country, the German soldiers encountered armed Estonian freedom fighters, who referred to themselves as "Forest Brothers" and had engaged in open combat against smaller Soviet units and supply lines since June 22, 1941. By August 1941, the Wehrmacht formed security units from these Estonian partisans to protect the German supply lines to the front. At the same time, the German Ordnungspolizei attempted to reorganize the Estonian police with volunteers. The Waffen-SS took advantage of the potential in the summer of 1942 and established the Estonian SS Legion in October of that year.