The attack on Poland was the Nazi regime’s first successful blitzkrieg offensive. The German armed forces, using coordinated air and land attacks, quickly broke through the Polish defensive lines and penetrated the interior of the country. The surrender of the capital, Warsaw (in Polish: Warszawa, as in the sign below), and the nearby fortress of Modlin on September 27-28, 1939, marked the end of the last major resistance attempt by the Polish army. The remaining units had surrendered by October 6. However, military resistance by nationalist and communist partisans continued until the end of the war.