'Operazione ''Malta-2''', which is otherwise called the 'Battle of Grand Harbour', was an Italian unsuccessful raid against Allied shipping in the harbour of Valletta, Malta (25/26 July 1941).

In this undertaking, Regia Marina commando frogmen of the 10a Flottiglia MAS attempted to penetrate the harbour to attack British shipping. The attackers destroyed the St Elmo Bridge as they attempted to enter the harbour before being driven off by the fire of the British coastal defences. The Italians suffered heavy casualties, including the death or capture of all the 10a Flottiglia MAS personnel involved.

Late in March 1941, men of the 10a Flottiglia MAS sank the British heavy cruiser York and a tanker off Crete during the 'Raid on Soudha Bay' using explosive-filled motor boats. Encouraged by this success, on 26 April the Italians ordered the 10a Flottiglia MAS to plan a similar attack on Grand Harbour. Night reconnaissance by motor torpedo boats during the new moon at the end of May got within 4 miles (6.4 km) of the British coastal defences without eliciting ant response.

The attack was authorised for the new moon period at the end of June as 'Operazione ''Malta-1'''. Motor torpedo boat reconnaissance during the night of 25/26 June approached to within 1.9 miles (3 km) of Grand Harbour without incident, and the first attempt was launched from Augusta in Sicily on the afternoon of 27 June with five motor torpedo boats towing nine MT explosive-filled boats and one MTS small motor torpedo boat, but the force was compelled to turn back by a deterioration of the weather. Another attempt was made on 29/30 June, but this too was aborted after delays imposed by poor weather and by problems with tow lines and engines.

The attack was rescheduled to 25/26 July as 'Operazione ''Malta-2''' using a plan modified as a result of the previous attempts. The number of MAS motor torpedo boats was reduced to two, in the form of MAS-451 and MAS-452. Two SLC human torpedoes were added, these being carried by a MTL-type manned torpedo carrier boat. The sloop Diana was added as a mother ship, and towed the MTL and carried nine MT and one MTS craft. One SLC was added as a stealthier method of making a hole in the steel anti-torpedo net suspended under the St Elmo Bridge: the net prevented the MT from passing into the Grand Harbour. The other SLC was to enter Marsamxett harbour and attack Allied submarines at Lazaretto Creek. The Regia Aeronautica would launch three air raids: those at 02.15 and 04.15 were to be navigational aids for the naval group, and that at 04.30, striking inland of Valletta, was to coincide with the opening of the steel net, diverting attention from and masking the noise of the naval group.

On the night of 23/24 July, a MAS patrol approached to within 1.25 miles (2 km) of the Maltese coast before the British turned on searchlights; the Italians were not seen.

Overall command was vested in Capitano di Fregata Vittorio Moccagatta in MAS-452, with Capitano di Corvetta Giorgio Giobbe commanding the MTs from the MTS. The SLC attacking the St Elmo Bridge net was to be piloted by Teseo Tesei, one of the SLC designers, and the other SLC by Franco Costa.

The two main fortifications at the entrance to the Grand Harbour were Fort Saint Elmo to the north at the tip of the Valletta peninsula, and Fort Ricasoli on the opposite southern shore. The forts were manned by the Royal Malta Artillery and armed with six and three 6-pdr guns respectively. The 1/Cheshire Regiment manned searchlights and machine guns along the Ricasoli shore.

In the middle of July, the British learned through 'Ultra' intelligence that the Italian were planning a minor naval raid on 'an island', and the timing of this Italian raid at the time of the 'Substance' major convoy operation from Gibraltar to Malta made the British wary of unusual Italian naval activity near Malta. On 24 June, the ships of the GM.1 convoy within 'Substance' reached Malta and became targets for the Italian raid.

The Italian force left Augusta, with 19 10a Flottiglia MAS personnel and 26 boat crew, at 18.15 on 25 July. The passage to the south benefited from good weather, but this also made it possible for the Royal Air Force radar at Fort Madalena to detect the Italian squadron at 22.30 at a distance of about 45 miles (72 km) to the north-east of Malta and alerted the defences. The alert lasted until a time after 23.00, when the radar echoes faded, although gunners and searchlight crews remained near their stations as a precaution. Diana detached her boats some 20 miles (32 km) to the north of Valletta between 23.00 and 00.00, then turned back to the north to await the raiders' return off Capo Passero. One MT was damaged during unloading. MAS-451 took over the task of towing the MTL. Almost immediately one of the MAS’s propellers became entangled in the tow line and the boats collided. One SLC, later used by Costa, was probably but unknowingly damaged, making this maiale (pig) difficult to control. The propeller could not be freed after an hour’s effort, and the tow was transferred to MAS-452, and MAS-451 was ordered to return to Sicily. Speed was increased to make up for lost time, but the damaged MT fell behind and was later scuttled. Half an hour later MAS-451 rejoined the group after finally freeing the entangled propeller.

The Italians were 5 miles (8 km) to the north of Valletta shortly after 02.00 on 26 July, and were thus 26 minutes behind schedule. The MAS remained here while the MTL and MT went forward at the MTL’s maximum speed of 5 kt. The planned air raids did not help navigation: the planned 01.45 attack did not take place, and the 02.45 raid by a single aeroplane missed Valletta and went unnoticed by the raiders. The MTs arrived 0.62 miles (1 km) off St Elmo shortly after 03.00, and here waited for the explosion at the bridge to signal he start of their attack. The MTL launched the SLCs about 220 yards (200 m) closer to shore, but the process took a considerable time and the Italians did not realise that the sea’s westerly current was pushing the stationary SLCs and MTs eastward and away from the bridge.

The damage to the SLC was discovered and, unable to repair it, Tesei ordered Costa to return to the MTL and scuttle the torpedo. Costa disobeyed his orders and attempted to carry out the attack starting at 03.45, about an hour behind schedule. By 04.30, Costa could not reach the bridge or demolish the net using the SLC’s detachable warhead and a time-delay fuse, and Tesei told Costa that an instantaneous fuse would be used if necessary. The third air raid, by two aircraft, took place earlier than planned, at 04.13, and served only to alert the defenders still further.

The MTs moved 545 yards (500 m) closer to the shore at 04.12, but no explosion occurred. At 04.40, Giorgio ordered two MTs forward to destroy the net. The first MT was moving too slowly and became snared in the net rather than breaking up and exploding; its pilot abandoned the boat as the attack went in and was later taken prisoner. The pilot of the second MT set the fuse to instantaneous, stayed aboard to ram the net at full speed, and was killed as both MTs exploded at 04.48. A bridge span collapsed, and its wreckage replaced the destroyed net as what was in fact a sturdier block. The explosion put the defences back onto full alert. Shortly after the explosion, a 6-pdr gun at Fort Saint Elmo fired at a tiny bow wake moving toward the bridge 600 yards (550 m) away, and caused the unidentified object to explode. This was probably the warhead of Tesei’s SLC, and how he was killed; an Italian breathing mask with hair and skin attached was discovered nearby in the morning.

The explosion at the bridge was the signal for the MTs to attack. and they were quickly illuminated by searchlights near the bridge and taken under intense fire. Two MTs were destroyed, their pilots being wounded and later taken prisoner. The remaining four MTs retreated to the north after the pilots had realised that they could not enter the harbour, and attempted to regroup. The British ceased firing near the bridge at 04.52. Two MTs, one with a wounded pilot overboard, remained near the edge of the illuminated area and within sight of the British. Initially, the boats were stationary and appeared abandoned, but at 05.20 the sudden movement of one toward the other caused the British to open fire once again. Both boats were destroyed, their pilots reaching shore and being taken prisoner. At about this time Giobbe reached the MAS boats: MAS-451 set course for Sicily, while MAS-452 took the MTS in tow and headed to the south, probably to rescue survivors.

Shortly after 05.30, 30 Hawker Hurricane single-engined fighters of Nos 126 and 185 Squadrons took off to hunt the Italian raiders. A Hurricane strafed MAS-452 and eight attacked the remaining pair of MTs. Both MTs were scuttled after the attack: one pilot died doing so, and the other swam to Malta and surrendered. The fighters were soon directed to the north to intercept 10 Macchi C.200 single-engined fighters of the 7o Gruppo, and a dogfight began at about 05.50. One Hurricane and two MC.200 aircraft were destroyed. Of the latter’s pilots, one was killed and the other was rescued by an Italian boat.

MAS-452 arrived 3.1 miles (5 km) off St Elmo shortly before 06.00, was spotted shortly after this and then came under fire from the fort. The boat was hit by a 6-pdr gun firing from beyond its theoretical maximum range: fired on a flat trajectory, the shell ricocheted off the surface of the water and exploded in the wheelhouse. Moccagatta, Giobbe, the rest of the 10a Flottiglia MAS's leadership, the boat’s commanding officer and the helmsman were killed. The remaining 11 crew members feared the MAS would sink, moved onto the MTS and returned to Sicily. MAS-452 was attacked by Hurricane fighters at about 06.20 some 36 miles (58 km) to the north-east of Malta. The boat was brought to a halt, and her fuel tank was hit and set on fire. Three crew members were killed. The nine remaining crew, including the wounded commanding officer, abandoned the boat, which exploded at 06.40, and were rescued by a Royal Army Service Corps launch later in the morning. The MTL had delayed escaping for too long, was spotted at 06.40 some 6 miles (9.7 km) to the north-east of Malta, came under attack by a Hurricane directed by gunfire from Fort Saint Rocco, and sunk. The pilot was wounded and captured. The mechanical difficulties with his SLC prevented Costa from making any progress; he and his crewmate scuttled the torpedo after the controls failed at 08.00 and then swam ashore near St Andrew’s and surrendered.

The pilot of the downed Hurricane paddled toward Malta in a dinghy before finding and boarding the abandoned MAS-452. The pilot’s enthusiastic waving the Italian flag attracted the attention of the RASC launch which had rescued the crew of MAS-452, but the launch was ordered to return to base upon reporting the 'aggressive' flag waving. The pilot was rescued at about 12.00 by a Fairey Swordfish single-engined floatplane.

The Italians had failed to achieve any of their objectives. None of the 19 10a Flottiglia MAS personnel escaped: 10 were killed and nine were taken prisoner. Of the 26 MAS crew men, six were killed, nine were taken prisoner and 11 escaped to Italy, where one later died of wounds. The pilot of one of the downed Italian fighters also died. Equipment losses included all of the boats and torpedoes except the MTS. Further 10a Flottiglia MAS operations were delayed by the loss of so many senior officers, but in December the unit raided Alexandria and crippled the battleships Queen Elizabeth and Valiant.

The British lost one Hurricane fighter, but captured MAS-452 (towed in by armed trawler Jade), one MT and Costa’s MAS-452 was renamed X-MAS and pressed into service as an RAF rescue launch and as a tender. The MT was sent to the UK for evaluation in September 1943.