This was an Allied unrealised plan for British forces to take the Italian island of Sardinia, by the time behind the Allied left flank in Italy in September or October 1943, with the French 'Firebrand' seizure of Corsica to follow about one month later (autumn 1943).
'Brimstone' (ii) and 'Firebrand' were just two of a raft of possible undertakings mooted at the time, others being the British 'Buttress' and 'Goblet' against Pizzo and Crotone, the US 'Musket' against Taranto, and the Allied 'Barracuda', 'Gangway' and 'Mustang' against Naples.
The plan was not pursued as the German forces on the island of Sardinia could make no significant impact on Allied operations in the Mediterranean theatre. The capture of the island had been envisaged first during the planning for the Italian campaign, an alternative to the campaign eventually undertaken (through Sicily and into southern Italy) being a 'left-hook' advance from Tunisia straight north into Sardinia before a double debouchment into northern Italy and, via Corsica, into southern France. The option was not adopted as the alternative offered safer maritime lines of communication and also provided the chance to draw German forces farther from the Normandy region scheduled for invasion in 'Overlord'.
As originally conceived, 'Brimstone' (ii) would have been executed by a British corps under the command of Lieutenant General F. E. Morgan and including Major General G. G. Simonds’s Canadian 1st Division, but its final form 'Brimstone' (ii) would have used more substantial Allied forces, in the shape of Major General Ernest W. Dawley’s US VI Corps (Major General Ernest N. Harmon’s 1st Armored Division, Major General Charles W. Ryder’s 34th Division and Major General Fred L. Walker’s 36th Division), Lieutenant General C. W. Allfrey’s British V Corps (Major General W. E. Clutterbuck’s 1st Division and Major General J. L. I. Hawkesworth’s 4th Division or Major General D. A. H. Graham’s 56th Division) and, in army reserve, Major General Matthew B. Ridgway’s US 82nd Airborne Division.
The whole plan was cancelled on 20 July 1943 after the success of 'Husky' (i) made Sardinia superfluous to current Allied requirements, and the island was later occupied in 'Norman'.