In the final days of August, Köln was stationed in the western Baltic to prevent Polish vessels from fleeing after the German invasion of Poland on 1 September; she was unsuccessful in this task.
在8月的最后几天，科隆号奉命驻扎在波罗的海西部，以防止波兰舰只在9月1日德国入侵波兰后出逃；但它未能完成这项任务。