French soldiers used the refectory containing The Last Supper as a stable in 1796.
French revolutionary forces took control of Milan that year and occupied Santa Maria delle Grazie’s refectory for military purposes. The room was used as an armory and stable, exposing Leonardo’s already deteriorating mural to rough treatment, dirt, and physical abuse. Accounts also describe soldiers throwing stones and scratching the eyes of the apostles.
The damage came after centuries of environmental decline. Leonardo had painted on a dry wall with an experimental tempera-based technique, so moisture and poor adhesion had already caused extensive flaking. A doorway cut through the mural in 1652 had also destroyed its lower center.
The 1796 episode is often mixed up with a separate disaster in 1800, when heavy rain caused flooding in the refectory. Water reportedly stood about two feet deep for 15 days, encouraging mold and further weakening the wall and paint.