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. Those defeats in turn made it more difficult for the Polish forces to fall back in an organized way to the secondary lines of defence (behind the Vistula and near the Romanian bridgehead).