Supply runs for Tobruk in 1941

Ships bringing supplies to Tobruk left ports in Egypt. The ships involved were generally small and they included the 40-knot fast minelayers. Some of the supply ships used sail power. The ships faced danger from air attack and from submarines. The wakes of ships at night were very visible in moonlight.
Captain Poland commanded the inshore squadron. He took command on 5 February 1941 and continued until the siege was lifted. At the beginning, the squadron included "two destroyers, three river gunboats and other small craft. They originally were employed for protecting shipping and for attacking enemy targets. Merchant ships entered and exited the Tobruk harbor both in daytime and nighttime. The Tobruk harbor accumulated ship wrecks over time.
Tobruk-bound shipping could not be protected by fighter aircraft. This was partly due to the scarcity of fighters and because the RAF had abandoned western airfields. The inshore squadron took heavy losses. Between 12 April 1941 and 1 June, they lost "a whaler, 2 armed boarding vessels, 2 minesweepers, a gunboat, a sloop and an anti-submarine trawler, and had four other ships damaged". Starting in early May 1941, the decision was made to employ ships of the 10th Destroyer Flotilla to carry supplies to Tobruk. The flotilla included five Australian destroyers. The first run was made on 5 May by two of the V-class destroyers. Once the battle for Crete commenced, destroyers were mostly involved in that operation.
Once the Germans had captured Crete, air attacks increased on shipping that was supplying Tobruk. Admiral Cunningham issued an order to only use destroyers on the run to Tobruk, and then only at night. That started as of 7 June 1941. The destroyers ran supply missions until 15 June, when Operation Battleaxe caused the end of the runs. They were restarted on 18 June. The Inshore Squadron now had four destroyers, three sloops, two gunboats, along with other smaller ships. They also now had some "A" Lighters, which were early landing craft. For a period, two destroyers would run into Tobruk, unload, and then leave during the night. This typically happened two nights out of three.
To send adequate supplies to Tobruk, slower ships had to supplement what was sent by destroyer. Supporting air power included "three Royal Air Force and two South African Air Force Squadrons. The closest air field for supporting Tobruk was one hundred  miles a way at Sidi Barrani. This is based on the account in Vol.III of the Australian Official History.