A bomb struck the refectory containing The Last Supper in 1943.
The Allied bombing occurred during World War II, on 15 August 1943, when Santa Maria delle Grazie in Milan was hit. Much of the refectory’s roof and surrounding structure was destroyed, but the wall bearing Leonardo’s mural survived. The painting had been protected with sandbags and other shielding, which helped prevent direct blast and shrapnel damage.
Survival did not mean the mural escaped unharmed. The destroyed roof exposed it to weather while rebuilding took place, and the vibration may have contributed to existing structural and paint problems. By then, The Last Supper was already fragile because Leonardo had painted on a dry wall using an experimental technique rather than durable wet fresco.
The event is sometimes misremembered as the painting being destroyed or struck directly. In fact, the refectory was badly damaged while the mural remained on the surviving wall. A major conservation campaign from 1978 to 1999 later stabilized the work and removed layers of earlier overpainting.