At 4:45 a.m. on September 1, 1939, the pre-dawn skies lit up over the Baltic Sea as the German battleship Schleswig-Holstein opened fire on a Polish fortress on the Westerplatte Peninsula as assault troops hidden aboard the vessel stormed the shoreline. The venerable ship that had seen action in World War I fired the first salvos of what would be a second global conflagration. Without a declaration of war, 1.5 million troops stormed Nazi Germany’s 1,750-mile border with Poland. They came from the north, south and west. They came by land, by air and by sea in a quest to regain territory lost by Germany in the Treaty of Versailles and colonize its neighbor.

Polish cavalry moves to the front to meet German invasion (Credit: Popperfoto/Getty Images)

The Nazis overwhelmed the antiquated Polish defenses with their blitzkrieg, or “lightning war,” tactics. German tanks steamrolled into the country. The Luftwaffe destroyed airfields, bombed passenger trains and mowed down civilians indiscriminately with machine-gun fire. Incendiary bombs torched Katowice, Krakow and the capital city of Warsaw. By sea, German warships and U-boats attacked the Polish navy. The 1 million-man Polish military was undermanned and underequipped. So antiquated were some army units that cavalry horses trotted to the front lines to confront the enemy’s mighty armored tanks.

German chancellor Adolf Hitler had rattled his saber at Poland for months. As he had done prior to the occupation of other countries, Hitler claimed that ethnic Germans were being persecuted inside Poland. Addressing the nation hours after the firing of the first shots, Hitler said he acted strictly in justifiable self-defense in response to Polish attacks on German soil the night before. Those attacks were not launched by Poland, however, but were carefully choreographed operations stage-managed by the Nazi propaganda machine as a pretext for an invasion. In the border town of Gleiwitz, S.S. operatives donned Polish military uniforms and seized one of Germany’s own radio stations and broadcast an anti-Nazi message in Polish. Prisoners from the Dachau concentration camp were dressed in Polish uniforms, brought to the radio station and shot to make it appear as if they were casualties of the firefight.

Hitler addresses the Reichstag on September 1, 1939 (Credit: Corbis)

“The Polish State has refused the peaceful settlement of relations which I desired, and has appealed to arms,” Hitler wrote of the phony attacks in his proclamation to the army. “In order to put an end to this lunacy, I have no other choice than to meet force with force from now on.”

Throughout the summer of 1939, Great Britain, France and the Soviet Union had carried on negotiations for forming a three-way alliance against Germany, but talks broke down over Poland’s refusal to grant Soviet troops the right to enter its territory, a demand the Polish military viewed as no more than a thinly veiled occupation. “With the Germans, we risk losing our freedom,” said Polish commander-in-chief Edward Rydz-Smigly, “with the Russians our soul.” The stymied Soviets instead pursued a separate peace with Germany, and the two countries signed a nonaggression pact on August 23 that contained a secret clause that divided Poland between them. With no threat of a Soviet intervention, Hitler believed he had a free hand to move against Poland. “The way is open for the soldier, now that I have made the political preparations,” he told his military commanders.

Still, Great Britain and France had guaranteed to fight in Poland’s defense, but many Nazi leaders, including foreign minister Joachim von Ribbentrop, believed history would repeat itself and the countries would back down. When Hitler remilitarized the Rhineland in 1936 in violation of the Treaty of Versailles, Britain and France did not respond militarily. When he annexed Austria two years later, the Western powers had no reply. When he annexed Czechoslovakia in 1939 in violation of the Munich Pact, which had already granted him the Sudetenland, Britain and France still did not respond with force.

This time, however, was different. Both Britain and France issued ultimatums for Germany to withdraw troops from Poland immediately or risk war. When Hitler learned of the British demand, he sat in stony silence before glaring at a surprised Ribbentrop and demanding to know, “What now?”

Credit: Popperfoto/Getty Images

On September 3 Britain and France declared war on Germany. Less than 20 years after “the war to end all wars,” the guns once again roared over a Europe that still bore deep scars from World War I. In spite of the declarations of war, little was done to stop the rapid German advance that had reached the outskirts of Warsaw by September 8. Britain was not prepared to launch a large military action, and French efforts were half-hearted along its eastern border with Germany.

Once the Soviet Union invaded Poland from the east on September 17, the country was squeezed in a vice grip that would last for 50 years until the fall of communism. By the end of September, Polish government and military leaders had fled the country, and the Nazis and Soviets had partitioned the country. A month after announcing the “counterattack” to the German people, Hitler declared victory on September 30, 1939.

Swastika flags now flew from public buildings. Resistors and Jews were rounded up and sent to concentration camps. Tens of thousands of Poles died in the invasion, the first of some 50 million men, women and children who would lose their lives in World War II. It was just the beginning of the suffering for the Polish people, who were victims of some of the greatest horrors in a monstrous war. Six million Poles, half of them Jewish, died during World War II at the hands of the Nazis and the Soviets. Even after the Red Army defeated Nazi forces in 1945, the brutality continued as Poland remained under the yoke of a totalitarian communist government until 1989.