Task: Question Understanding
Input (English): Context : Virtually all battles that are considered part of the 'Battle of the Border' (with the exception of the Battle of Hel, which lasted for more than a month and the Battle of Mokra, a Polish defensive victory) resulted in rapid defeat of Polish forces, which were forced to abandon the regions of Pomerania, Greater Poland and Silesia. 
Question : When did Battle of the Border occur?
Output (English): point in time