Excerpts from Books and Wikipedia
"The siege of Vienna ended in 1529 and was the climax of Ottoman incursions into Europe. Rivalry between King Francis I of France and Holy Roman Emperor Charles V had weakened sixteenth-century Europe. Ottoman Sultan Suleiman I 'the Magnificent' had taken advantage of the divisions to capture Buda and make Hungary a vassal state. Alarmed, Archduke Ferdinand of Austria encouraged a Hungarian revolt in 1528, while Suleiman was in Persia. . . . The Austrians had a force of 22,000 infantry, 2,000 cavalry, and 72 cannons. The Ottomans numbering some 350,000 men arrived at Vienna on September 26, but abandoned their siege guns, bogged down along the muddy roads. The Turks laid mines under the walls and Austrian pikemen beat back the attacks of the janissaries--Turkish cavalry composed of Christian converts sold into slavery and trained as sacrificial warrior elite. On October 14, having lost 20,000 troops, Suleiman ordered a final push. But a massive mine collapsed the wall outward, blocking the attacker's path. The assault was over. . . . The Ottoman failed to invade Vienna again in a siege of 1683 . . ." [1001 Days]