Operation Shingle (January 22, 1944) was an Allied amphibious landing in the Italian Campaign against German forces in the area of Anzio and Nettuno, Italy. The operation was commanded by American Major General John P. Lucas and was intended to outflank German forces of the Winter Line and enable an attack on Rome. The resulting combat is commonly called the Battle of Anzio.

The success of an amphibious landing at that location, in a basin substantially comprising reclaimed marshland and surrounded by mountains, depended completely on the element of surprise and the swiftness with which the invaders could move relative to the reaction time of the defenders. Any delay could result in the occupation of the mountains by the defenders and the consequent entrapment of the invaders. Lieutenant General Mark Clark, commander of the U.S. Fifth Army, understood that risk, but Clark did not pass on their appreciation of the situation to his subordinate General Lucas who preferred to take time to entrench against an expected counter attack. The initial landing achieved complete surprise with no opposition and a jeep patrol even made it as far as the outskirts of Rome. Despite that report, Lucas, who had little confidence in the operation as planned, failed to capitalise on the element of surprise by delaying his advance until he judged his position was sufficiently consolidated and his troops ready.