On this day in 1944, Allied forces begin a major assault on the Gustav Line, a German defensive line drawn across central Italy just south of Rome.
The Gustav Line represented a stubborn German defense, built by Field Marshal Albert Kesselring, that had to be broken before the Italian capital could be taken; the attack on the line was also part of a larger plan to force the Germans to commit as many troops to Italy as possible in order to make way for an Allied cross-Channel assault—what would become D-Day. With the Eighth Army's 1,000 guns, the Fifth Army's 600, and more than 3,000 aircraft, the Allied forces, which included British, French, Indian, Moroccan, and Polish corps, opened fire in a barrage of artillery from Cassino to the Mediterranean Sea. Despite the fact that the Allies outnumbered the Germans by a ratio of 3 to 1, it took seven days before the Gustav Line could be broken, with the Polish Corps occupying the famed Benedictine abbey of Monte Cassino. The Germans withdrew, to the Hitler Line, but that too was penetrated. The Allies would be in Rome by June 4.