The Germans established the Gustav Line centered on Monte Cassino to block an Allied northward advance on Rome. By spring 1944, three major ground assaults had failed to breach this line, and even the amphibious landing at Anzio in January 1944 had failed. Lieutenant General Ira C. Eaker, commander of the Mediterranean Allied Air Forces, decided to launch a supply interdiction operation to break the stalemate and force a German withdrawal.
Operation strangle was directed mainly against the Italian rail system, Germany's primary means of supply transportation, but it also encompassed ports and bridges. The campaign involved an interdiction belt running across Italy from east to west as far north of the Gustav Line as possible to force the Germans to use alternate transport means to the front. Medium bombers of the U.S. Army Air Force's Twelfth Air Force and British First Air Force began operations on 19 March, and the strongly escorted daylight raids continued until 11 May 1944. The bombers succeeded in inflicting substantial damage on the rail system, cutting the lines more than 100 times each day and coming close to closing down all rail traffic 100 miles north of Rome. Nonetheless, the operation failed to force the Germans to withdraw from the Gustav Line in order to shorten their supply lines.
The campaign failed for four principal reasons. First, there were no significant ground operations during this period, and the aerial campaign was thus unsupported by other arms. Second, the Allies significantly overestimated (by a factor of close to 10) German supply requirements while they were in the static defenses of the Gustav Line, especially in the absence of any serious ground actions. Third, the German army minimized the effects of the campaign against the rail system through rapid repair of damage and construction of bypasses around destroyed rail sections, imposition of stricter rationing, movement at night, and diversion of scarce motor vehicles to transport supplies. Finally, the Allies could not deploy an adequate night bombing force, which prevented their air forces from neutralizing the Germans' very effective countermeasures.
By the end of April, the Allies determined that airpower alone would not force a German withdrawal from the Gustav Line, and they launched Operation diadem on 11 May. The operation combined an aerial interdiction campaign against supply lines with a ground offensive. This air offensive was focused closer to the immediate German rear areas and also targeted their operational reserves and major command-and-control facilities. Within less than a month, Allied ground forces penetrated the Gustav Line, linked up with the Anzio beachhead, and captured Rome on 4 June.
Paul E. Fontenoy
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