Allies bombed a 1,400-year-old monastery believing Germans were using it as an observation post. The Germans weren't — but they moved into the ruins the moment the bombing stopped.
Monte Cassino was a Benedictine abbey founded in 529 AD, perched on a hill commanding the Liri Valley — the only viable road to Rome. German forces had fortified the surrounding Gustav Line with concrete bunkers, gun emplacements, and minefields. To advance on Rome, the Allies had to break through this position. Four attempts over four months would be required.
The most controversial decision of the Italian campaign came on February 15, 1944. Believing the ancient monastery was being used as a German observation post, Allied commanders ordered its destruction. 254 bombers dropped 1,400 tons of explosives on the abbey, reducing it to rubble. Post-war evidence showed no German troops were inside at the time — German commanders had specifically ordered the monastery protected. The bombing killed approximately 230 Italian civilians sheltering inside.
The rubble made things worse. German paratroopers immediately occupied the ruins after the bombing, finding the broken walls and caves far easier to defend than an intact building. The ruins provided perfect cover. Three more costly assaults failed to dislodge them. Each Allied attack — British, American, New Zealander, Indian, French — ran into the same grinding wall of fire.
The nationalities fighting at Cassino formed one of the most diverse coalitions of the war: New Zealanders, Indians, Gurkhas, Poles, Free French, Moroccans, Algerians, Americans, and British all cycled through the battle. The French Expeditionary Corps, including Moroccan Goumiers, achieved some of the most impressive advances by outflanking through terrain German planners had considered impassable.
The decisive breakthrough came in Operation Diadem on May 11, 1944. A coordinated assault by 20 divisions along a 32-kilometer front finally cracked the Gustav Line. Polish forces of the II Corps, who had fought their way from Siberia through the Middle East to Italy, were given the honor of attacking Monte Cassino itself. On May 18, a Polish bugler sounded the call from the ruins of the monastery. The flag went up at 10:20 a.m.
The road to Rome opened, and Allied forces entered the city on June 4, 1944 — only to be immediately overshadowed by the news two days later of D-Day in Normandy. The Italian campaign, with all its sacrifice and controversy, slipped from the headlines. The battles at Cassino had cost an estimated 55,000 Allied and 20,000 German casualties, all for an advance that took four months and three failed attempts.