'MB1' was a British two-part naval gunfire bombardment of Italian targets on the Libyan coast of North Africa by elements of Admiral Sir Andrew Cunningham’s Mediterranean Fleet (20/24 August 1940).
The operation got under way on 20 August as the gunboat Ladybird departed Alexandria toward Mersa Matruh, and two days later the destroyers Diamond, Ilex, Juno and Australian Stuart and Waterhen followed, with heavier supported provided by the Australian light cruiser Sydney. Most of the destroyers shelled the Italian seaplane base at Bomba near Tobruk on 23 August, but Waterhen had been detached to cover the gunboat Ladybird after the latter had shelled Bardia on 24 August.
On the previous day the torpedo-armed Fairey Swordfish aircraft of the FAA’s No. 813 Squadron had moved forward from Dekheila to Sidi Barrani as a forward base, and nine of the aircraft launched their torpedoes against shipping at Tobruk while the RAF’s No. 211 Squadron provided reconnaissance and eleven of its aircraft attacked the airfield, and 12 fighters of the RAF’s No. 33 Squadron patrolled over the target. Seven torpedoes dropped inside the harbour: the destroyer Zeffiro was sunk and the destroyer Euro holed forward, two merchant vessels (the 3,955-ton Manzoni and 5,000-ton Serenitas) were sunk, and the 15,000-ton liner Liguria was damaged. All the aircraft returned safely.
While this attack was taking place the Mediterranean Fleet’s 3rd Cruiser Squadron (light anti-aircraft cruiser Capetown and light cruiser Caledon), escorted by four destroyers, steamed as far to the west as Bardia to bombard Italian shipping in that port and to provide support for any returning aircraft in distress. The British ships opened fire at a range of 9,000 yards (8230 m) at dawn on 6 July, and hit to military supply ships. Italian aircraft attacked the British warships as they returned toward Alexandria, but caused no damage.