World War II: Allied forces launch the first of four assaults on Monte Cassino with the intention of breaking through the Winter Line and seizing Rome, an effort that would ultimately take four months and cost 105,000 Allied casualties.

The Allies, formally referred to as the United Nations from 1942, were an international military coalition formed during World War II (1939–1945) to oppose the Axis powers. Its principal members were the "Big Four" – the United Kingdom, United States, Soviet Union, and China.

The Battle of Monte Cassino, also known as the Battle for Rome, was a series of four military assaults by the Allies against German forces in Italy during the Italian Campaign of World War II. The objective was to break through the Winter Line and facilitate an advance towards Rome.

The Abbey of Monte Cassino is a Catholic, Benedictine monastery on a rocky hill about 130 kilometres (80 mi) southeast of Rome, in the Latin Valley. Located on the site of the ancient Roman town of Casinum, it is 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.

The Winter Line was a series of German and Italian military fortifications in Italy, constructed during World War II by Organisation Todt and commanded by Albert Kesselring. The series of three lines was designed to defend a western section of Italy, focused around the town of Monte Cassino, through which ran the important Highway 6 which led uninterrupted to Rome. The primary Gustav Line ran across Italy from just north of where the Garigliano River flows into the Tyrrhenian Sea in the west, through the Apennine Mountains to the mouth of the Sangro River on the Adriatic coast in the east. The two subsidiary lines, the Bernhardt Line and the Hitler Line, ran much shorter distances from the Tyrrehnian Sea to just northeast of Cassino where they would merge into the Gustav Line. Relative to the Gustav Line, the Hitler Line stood to the northwest and the Bernhardt Line to the southeast of the primary defenses.