After news of the Soviet invasion of Poland reached General Dab Biernacki and his officers, all units of the Northern Front were ordered to march southwards, to the area of Tomaszów Lubelski, to join Kraków Army and Lublin Army. All Polish forces tried to fight their way to Lwów and the Romanian Bridgehead. The Wehrmacht, well aware of it, tried to halt Polish advance in the Battle of Tomaszów Lubelski.