The German offensive proved the folly of the border defense plan in the first days of the war. Army Pomorze was defeated in the battle of Bory Tucholskie, and forced to retreat towards the south-east. Army Poznań, meanwhile, although not facing heavy German assaults, was forced to retreat east due to defeats of its neighbours (Army Pomorze in the north and Army Łódź in the south); both of them were retreating, meaning that Army Poznań was in danger of being flanked and surrounded by the German forces. On 4 September, Army Poznań moved through Poznań and abandoned it to the enemy, although at this point it was not in contact with any significant German forces. By 6 September, Armies Pomorze and Poznań had linked, forming the strongest Polish operational unit in the campaign, and general Bortkowski accepted the command of general Kutrzeba.