The British had expected that the enemy air forces would attack the relief convoys that were carried out as part of Operation Supercharge. The attacks either did not occur or were ineffective. The only air attack occurred on 19 September 1941 on a convoy of landing craft coming from Mersa Matruh with a cargo of tanks. At this point in the war, the landing craft were called "lighters". Bombs were dropped by the attacking aircraft, but they fell into the sea about a half a mile from the landing craft. The only problems encountered during Operation Supercharge occurred when the small craft involved had some defect that prevented them from sailing to Tobruk. The day after the air attack, there were three schooners had sailed for Tobruk. None of them arrived at Tobruk due to various problems.
During Operation Supercharge, not quite six thousand men were transported out of Tobruk. This number included 544 wounded soldiers. Their replacements in the number of 6,300 men arrived at Tobruk. The operation interfered with supplies for Tobruk, so more than 1,000 tons less than had arrived during July and August 1941. This was partly due to the destroyers having to make room for soldiers and partly because the landing craft were carrying tanks rather than supplies. They also had restricted shipping to and from Tobruk to periods when the RAF could provide air cover.
Shipping traveling to Tobruk was stopped pending a conference to be held on 30 August to discuss supplies for Tobruk. Shipping continued to be suspended for a time following the conference.
The importance of restricting convoys to days when there was no moon was demonstrated on the night of 8 to 9 September when a convoy of destroyers ran in to Tobruk during time when there was moonlight. The destroyers were bombed while entering the Tobruk Harbor and when they departed. Two of the destroyers narrowly missed being hit by bombs. As soon as three days later, another convoy sailed when there was moonlight and it was bombed very early in the day.
Tobruk needed some 1,500 tons of supplies per day. That included about 20 tons a day of petrol. The supply that arrived averaged about 32 tons a day less than was needed. The situation was actually better than the figures would indicate, because "actual ration strength" was less than the nominal figure of 25,000 that was used for planning. This is based on the account in Vol.III of the Australian Official History.