対潜戦
Anti-submarine warfare (ASW) operations were also executed by the allied navies during Operation Grand Slam. However, a French submarine successfully penetrated the destroyer screen protecting the American-French carrier task force and successfully sank a target within that formation. That French submarine was subsequently declared to be heavily crippled by ASW forces. Finally, a surface force consisting of eight cruisers and ten destroyers carried out a shore bombardment off the Sardinian coast.