The Battle of Bzura was a significant military engagement during the early stages of World War II, occurring from September 9 to September 22, 1939. It involved the forces of Poland attempting to halt the advance of the Nazi German army as they invaded Poland. The battle took place near the Bzura River and was marked by intense fighting, with Polish troops launching a counteroffensive against the Germans. Despite initial successes, the Polish forces were ultimately overwhelmed by the superior numbers and tactics of the Germans. The battle resulted in heavy casualties for the Polish side and contributed to the rapid fall of Poland in the war. The defeat at Bzura was part of the larger Invasion of Poland, which began on September 1, 1939.