'Buttress' was a British unrealised plan for an amphibious invasion of southern Italy in the area of the Gulf of Goia (27 July/4 September 1943).
As such, 'Buttress' was just one of many contingency plans evolved by several temporarily uncommitted formation headquarters of General Dwight D. Eisenhower’s Allied Forces in North Africa command at the behest of General George C. Marshall, the US Army chief-of-staff.
'Buttress' was the responsibility of Lieutenant General B. G. Horrocks’s X Corps of General Sir Bernard Montgomery’s 8th Army, which was not involved in the 'Husky' (i) campaign in Sicily and thus available for a major landing in the 'toe' of Italy. The 'Buttress' scheme envisaged ships of the 11th Amphibious Force landing, in the Reggio di Calabria and San Giovanni area of the Gulf of Goia opposite Messina in Sicily, of Major General G. W. E. J. Erskine’s 7th Armoured Division, Major General J. L. I. Hawkesworth’s 46th Division and Major General D. A. H. Grahame’s 56th Division for an advance to the north-east along the north coast of the 'toe', supported after about one month (necessary for the reassembly of the theatre’s limited amphibious forces) by 'Goblet' to be undertaken at Crotone on the 'ball' of the Italian foot by Lieutenant General C. W. Allfrey’s V Corps.
These plans were created in the absence of any significant knowledge of Axis defensive capabilities in the south of Italy, although these were assumed to be strong. After the successful launch of 'Husky' (i) and the revelation that the Axis defence was not as powerful as had been feared, however, the caution that had characterised the planning for 'Buttress', in the form of only a short 'hop' across the Strait of Messina, was overtaken by enthusiasm for a landing or landings considerably farther to the north on the 'foot' or even the 'leg' of Italy.
It was eventually decided, however, that the X Corps (now commanded by Lieutenant General Sir Richard McCreery) would be loaded with a view to participation in 'Avalanche' as a possible alternative to 'Buttress'. With the success of 'Baytown' (i), 'Buttress' was cancelled on 4 September and the X Corps was then allocated to 'Avalanche'.