07/09/1939: Polish forces trying to hold the line at the Narew River, start to collapse. Krakow surrenders to German troops. The German 10th Army closes ever nearer to Warsaw. A deeper defensive line is prepared by the Poles at the Bug River, as their battered armies begin a withdrawal toward that line. The BBC commences daily radio broadcasts in Polish.
http://www.worldwar-2.net/timelines/war-in-europe/eastern-europe/eastern-europe-index-1939.htm
