Site of the Roman town of Casinum, it is widely known for its abbey, the first house of the Benedictine Order, having been established by Benedict of Nursia himself around 529. It was for the community of Monte Cassino that the Rule of Saint Benedict was composed.

Allied Forces assumed that the Germans were using Monte Cassino as a fortified position and observation post. Even ambiguous information regarding the German's location was believed to be valid.