After a week of war, the German invasion of Poland ran according to plans. German troops of the 8. Armee were marching eastward on Warsaw, and on the other side of the Bzura river were Polish troops withdrawing in the same direction. Stretched along the Bzura, protecting the army's flank, was the 30. Infanterie-Division. On the morning of 9 September, the Polish Knoll-Kownacki Operational Group launched a large-scale assault across the Bzura. For the first (and would it prove later, only) time during the 1939 conflict the Poles mounted an offensive.