Port Chalmers carried 250 members of the Royal Artillery one light, one heavy anti-aircraft regiment and thirty field guns to strengthen the island against airborne assault.

The Perla-class submarine Diaspro found the convoy on 22 July and launched torpedoes which narrowly missed Renown and HMAS Nestor.

The merchant ship, carrying 484 army officers and men as passengers along with the crew, came to a dead stop as it took on water.

[7][a] The six merchant ships of Convoy GM 1 arrived in Malta on 24 July where they were observed by a CANT Z.506 reconnaissance seaplane, escorted by 42 Macchi C.200 fighters.

[2] The Raid on Grand Harbour, an audacious attack by the elite Decima MAS, using explosive motor-boats (MTM) and manned torpedoes early on 26 July was thwarted by Radar and Ultra, ending in disaster for the Italians.