Strategic Setting

Following the successful Allied landings at Calabria, Taranto, and Salerno in early September 1943 and the unconditional surrender of Italy that same month, German forces had quickly disarmed their former allies and begun a slow, fighting withdrawal to the north. Defending two hastily prepared, fortified belts stretching from coast to coast, the Germans significantly slowed the Allied advance before settling into the Gustav Line, a third, more formidable and sophisticated defensive belt of interlocking positions on the high ground along the peninsula's narrowest point. The Germans intended to fight for every portion of this line, set in

the rugged Apennine Mountains overlooking scores of rain-soaked valleys, marshes, and rivers. The terrain favored the defense and, as elsewhere in Italy, was not conducive to armored warfare. Luftwaffe Field Marshal Albert Kesselring, whom Hitler had appointed as commander of all German forces in Italy on 6 November 1943, promised to hold the Gustav Line for at least six months. As long as the line was maintained it prevented the Fifth Army from advancing into the Liri valley, the most logical and direct route to the major Allied objective of Rome. The validity of Kesselring's strategy was demonstrated repeatedly between October 1943 and January 1944 as the Allies launched numerous costly attacks against well-entrenched enemy forces.

The idea for an amphibious operation near Rome had originated in late October 1943 when it became obvious that the Germans were going to fight for the entire peninsula rather than withdraw to northern Italy. The Allied advance following the Salerno invasion was proving so arduous, due to poor weather, rough terrain, and stiffening resistance, that General Dwight D. Eisenhower pessimistically told the Anglo-American Combined Chiefs of Staff that there would be very hard and bitter fighting before the Allies could hope to reach Rome. As a result, Allied planners were looking for ways to break out of the costly struggle for each ridge and valley, which was consuming enormous numbers of men and scarce supplies. When the British conducted a successful amphibious operation at Termoli on 2-3 October, landing behind German positions on the Adriatic front, hopes were raised that a similar, larger assault south of Rome could outflank the Gustav Line. Such an operation could facilitate a breakthrough along the main line of resistance in the south and cut German lines of retreat, supply, and communications. On 8 November British General Sir Harold R. L. G. Alexander, commander of the 15th Army Group (consisting of the Fifth and Eighth Armies under Lt. Gen. Mark W. Clark and General Sir Bernard L. Montgomery, respectively), passed down orders to Clark from the Combined Chiefs of Staff. They directed him to formulate a plan for landing a single division at Anzio (code-named Operation SHINGLE) on 20 December 1943 as part of a projected three-pronged Allied offensive. The subsequent lack of progress, however, and a chronic shortage of troops and shipping due to the ongoing buildup for the cross-Channel invasion of France (OVERLORD), soon made the initial landing date impractical.