This was the Allied air offensive designed to cut the maritime, road and rail lines of communication in Italy to the German armies in the area to the south of Rome (19 March/11 May 1944).
The object of this major undertaking was to destroy the capacity of the Germans to move supplies, fuel, matériel and reinforcements to the south of a line between Pisa and Rimini, and thus achieve the strategic goal of eliminating or greatly reducing the need for an Allied ground offensive on the region. Although the initial goal of forcing the Germans to withdraw was not achieved, the air interdiction of 'Strangle' played a major part in the success of the Allies' subsequent 'Diadem' ground offensive to break though the 'Gustav-Linie' defences during the spring and early summer of 1944.
During 'Strangle', two principal interdiction lines were maintained across the narrow boot of Italy. This meant that no through trains were able to run to the south from the Po river valley to the front, and that in the area to the south of Florence all German supplies had to be moved by truck. To achieve its task, 'Strangle' employed medium bombers and fighter-bombers over an area of 150 sq miles (390 km²) from Rome to Pisa and from Pescara to Rimini.
Under the overall supervision of Lieutenant General Ira C. Eaker, commanding the Mediterranean Allied Air Forces, the two main Allied air formations involved in the campaign co-ordinated by Major General John K. Cannon’s Mediterranean Allied Tactical Air Force were Brigadier General Gordon P. Saville’s XII Air Support Command of Cannon’s own US 12th Army Air Force and Air Vice Marshal H. Broadhurst’s Desert Air Force of the Mediterranean Allied Tactical Air Force, supported by Major General Nathan F. Twining’s US 15th Army Air Force of Twining’s own Mediterranean Allied Strategic Air Force.
During the campaign some 20,000 tons of bombs were delivered on targets such as railway defiles, marshalling yards, bridges and tunnels, and though some useful results were achieved (some 10 major supply arteries being cut), these were insufficient to prevent the Germans moving adequate forces and resources to check the Allies’ May 1944 offensives. During March, for example, the forces under the commander of the Oberbefehlshaber ‘Südwest’, Generalfeldmarschall Albert Kesselring, received a daily ration of 1,357 tons of supplies (compared with a requirement of 2,261 tons), and the expedients adopted by the Germans to ensure continued supplies seriously eroded their reserves of motor fuel.
'Strangle' had achieved Allied air superiority before the start of 'Diadem', in the course of which Allied air commanders continued the interdiction of the German lines of communication and supply, and also undertook close air support to maintain air superiority. Some changes in target selection proved to have far-reaching effects on later military doctrine: a partial switch from rail to road targets, coupled with a concentration on the region closest to the German lines, aimed to cripple the Germans by denying them reliable transportation and reducing access to local supplies.
These efforts reduced but did not wholly deny the Germans access to fuel and ammunition. The Germans proved themselves to be particularly adroit in the discovery and use of alternative routes, and also in their ability to effect quick repairs of damaged points, especially at night and in bad weather, when Allied aircraft were grounded. German supply needs were low during 'Strangle', moreover, so in some respects they were able to maintain and even increase supplies.
The major benefit of 'Strangle' to the Allies was in fact unintended: it significantly reduced German troop mobility. The Germans had been unable to mass adequate reserve forces behind the front and therefore placed great reliance on tactical mobility, especially laterally across the front, so their inability to transfer forces quickly to threatened points exercised a decidedly adverse effect on their battle readiness. Three weeks after the start of the 'Diadem' ground offensive, therefore, the Germans were in full retreat.