'Treacle' was a British naval undertaking to replace Major General Leslie J. Morshead’s Australian 9th Division as the garrison of beleaguered Tobruk, on the coast of North Africa, with Major General R. M. Scobie’s British 70th Division, Generał brygady Stanisław Kopański’s Polish Independent Carpathian Brigade, and the Czechoslovak 11th Battalion – East under Scobie’s overall command (21/27 August 1941).
The operation began on 19 August as the first of an eventual 6,000 men were ferried to Tobruk, covered by the cruisers of the 7th and 15th Cruiser Squadrons.
On the first night the destroyers Hasty, Jervis and Kimberley departed Alexandria for Tobruk in the first lift, and arrived back at Alexandria on 20 August. On this day, the light cruisers Ajax and Neptune departed Alexandria to cover the cruiser minelayer Latona and destroyers Kingston, Kipling and Australian Nizam to Tobruk in the second lift.
The third lift, which departed Alexandria on 21 August, involved the destroyers Griffin, Jackal and Kandahar, which returned to Alexandria on the following day. On the same day, while returning from the second lift, Nizam came under attack from Junkers Ju 88 bombers of Hauptmann Karl-Friedrich Knust’s III/Lehrgeschwader 1 to the north of Bardia, and the destroyer was damaged by a near miss. Kingston took Nizam in tow until the damaged destroyer could make headway under her own power once more, and Ajax and Neptune provided cover for the destroyer’s return to Alexandria.
On 22 August the cruiser minelayer Abdiel and destroyers Hasty, Jervis and Kimberley departed Alexandria on the fourth lift, and the light cruiser Galatea and light anti-aircraft cruisers Naiad and Phoebe of the 15th Cruiser Squadron covered the ships carrying troops. The ships arrived back at Alexandria on 23 August.
On 24 August Ajax and Neptune departed Alexandria to cover Latona, Griffin, Kingston and Kipling making the fifth lift, and all the ships arrived back at Alexandria on the following day.
On 25 August Galatea, Naiad and Phoebe again departed departed Alexandria to cover Abdiel, Hasty, Jackal and Kandahar as they undertook the sixth lift. The light cruisers came under unsuccessful attack at dusk on this day, but all the ships safely returned to Alexandria on the following day.
Ajax and Neptune departed Alexandria on 26 August to escort Latona, Griffin, Havock and Jervis on the seventh lift, and all the ships arrived back at Alexandria on 27 August. One this day Galatea, Naiad and Phoebe once again departed Alexandria to cover Abdiel, Hotspur, Kingston and Kipling on the eighth lift, and the latter four ships returned independently to Alexandria, arriving on 28 August.
On the day before this, Savoia-Marchetti SM.79 torpedo bombers of the Italian air force had attacked Phoebe and damaged her severely with air-launched torpedoes in the area to the north of Sidi Barrani. Hasty, Jervis, Kandahar and Kimberley were despatched from Alexandria to escort the damaged cruiser, which was able to proceed to Alexandria under her own power and, after temporary repairs had been effected, sailed to the USA for permanent repairs.
On 28 August Ajax and Neptune departed Alexandria to escort Latona, Decoy, Jackal and Napier on the ninth lift, and all the ships arrived back at Alexandria on the following day, when Griffin and Havock departed Alexandria for the tenth and last lift before returning to Alexandria on 30 August.
Although the operation had succeeded in its primary task, the naval forces had suffered comparatively heavy losses.
On the same day that Phoebe was damaged, off Tobruk, a Junkers Ju 87 dive-bomber sank the anti-submarine whaler Skudd III.