The Thirty Years’ War had been raging in what is now Germany for a dozen years when, in 1630, its scope widened to include international actors. Foremost among them was King Gustavus Adolphus of Sweden, who landed a large invasion force in support of the Protestant cause in June 1630. In turn the forces of the imperial Catholic League moved on Magdeburg, a strategic port city on the Elbe River, to make it a base of operations for fighting the Swedes. The imperial army’s sack of the city began with a blockade in November 1630 and culminated on May 20, 1631, in what became known as the most infamous episode of the war.
Magdeburg had been under a loose imperial blockade, commanded by Count Gottfried Heinrich von Pappenheim, since November 1630. Gustavus Adolphus had given Magdeburg assurances of protection, and when Count Johann Tilly led a substantial army to besiege it in earnest on April 3, Gustavus Adolphus moved to protect the city. He had sent one of his officers, Dietrich von Falkenburg, to command the defense. Tilly had a powerful siege train and methodically destroyed the city’s outer fortifications.
By May 1, Tilly had taken all of Magdeburg’s outer defenses. Two days later the suburbs fell, and the city was reduced to its inner defenses. Gustavus Adolphus was unable to reach Magdeburg because local rulers along the way were unwilling to allow him to march through their territories. Although desperate, Magdeburg still refused to surrender. On the morning of May 20, Tilly launched his final charge. Within two hours his infantry had breached the inner defenses, followed by heavy cavalry. During the attack, fires broke out across the city, and imperial soldiers began to massacre the citizenry and loot the city. Tilly, unable to control his men, lost all of the supplies he had hoped to gain. By day’s end, 20,000 of Magdeburg’s inhabitants had been killed—the single greatest tragedy of the war.
News of the massacre spread quickly through Protestant Europe, providing a rallying cry against Catholics. Soon after the sack of Magdeburg, Gustavus Adolphus gained new Protestant allies such as the Elector of Brandenburg, further widening the war and swelling the Protestant army to more than 175,000 soldiers.
Losses: Protestant, 20,000 defenders and civilians of 25,000; Imperial, 300 dead and 1,600 wounded of 25,000.