"On January 22 the Allied VI Corps landed on the beaches near Anzio, 33 miles (53 km) south of Rome. The assault force included the U.S. 3rd Division, British 1st Division, and U.S. Rangers. In 24 hours the Allies landed 36,000 troops and 3,000 vehicles and took control of Anzio and the neighbouring town of Nettuno.
Only two German battalions were present in the area, and a swift dash inland could have seized the Alban Hills—covering the immediate approach to Rome—or even Rome itself. However, the Allies’ plan had been based on the calculation that the Germans would immediately counter the landing. Thus, they were primarily concerned with consolidating the beachhead, while the main forces in the south were to take advantage of the anticipated weakening of the enemy’s resistance there. The Germans did not react in the way expected.
When the lack of opposition near Anzio became clear, Gen. Harold Alexander, head of the Anglo-American Fifteenth Army Group, wished to quicken the move inland. VI Corps commander Gen. John P. Lucas opted for a more cautious approach, however, and no serious advance was attempted for more than a week. This allowed Kesselring ample time to switch his reserves to the scene, while he also held in check the forward drive of the main Allied forces on the Cassino sector. By the end of January, the VI Corps had been sealed in. On February 3, the 12th day after the landing, the Germans developed a powerful counteroffensive against the Allied position at Anzio. This in turn was checked, but the Allied force was left in an awkwardly shallow and narrow bridgehead."