At dawn on September 1, 1939, Nazi Germany invaded Poland, launching a conflict that would ignite World War II. German forces struck with overwhelming speed and precision, deploying more than 60 divisions and 1,300 aircraft in a blitzkrieg that overwhelmed Poland’s defences. The assault began with naval bombardments near Gdańsk and rapid advances from East Prussia, Silesia, and Slovakia. Despite determined resistance and even a counterattack near the Bzura River, Poland’s army could not withstand the modernised German war machine.