Axis advance of to the Egyptian frontier in early 1941, increased the road transport distance for supplies to . Benghazi was captured in April but coastal shipping could only carry and the port was within range of the DAF. Tobruk could take about per day but lack of shipping made its capture irrelevant. A German motorised division needed per day and moving the supplies two-ton lorries. With seven Axis divisions, air and naval units, of supplies per month were needed. Vichy France agreed to Bizerta being used for supplies but none passed through until late 1942. From February–May 1941, a surplus of was delivered; attacks from Malta had some effect but in May, the worst month for ship losses, of supplies arrived. Lack of transport in Libya left German supplies in Tripoli and the Italians had only for deliveries to A record amount of supplies arrived in June but at the front, the shortages worsened. There were fewer Axis attacks on Malta from June and ships sunk increased from in July, to in September, when Benghazi was bombed and ships diverted to Tripoli; air supply in October made little difference. Deliveries averaged per month from July–October but the consumption of of fuel deliveries by road transport and truck unserviceability of reduced deliveries to the front. In November, a five-ship convoy was sunk during Operation Crusader and ground attacks on road convoys stopped journeys in daylight. Lack of deliveries and the Eighth Army offensive, forced a retreat to El Agheila from 4 December, crowding the Via Balbia where Allied ambushes destroyed about half of the remaining Axis transport. Tobruk Work on the fortifications at Tobruk had begun in March, using the Italian defences, two lines of concrete bunkers away from the port, making a perimeter about long, far enough out to keep artillery out of range of the port. Few intermediate defences had been built by the Italians except at the Bardia–El Adem road junction, the barbed wire was in disrepair and an anti-tank ditch was unfinished. The Allies selected another line about back from the perimeter and worked on this while the original line was refurbished. Two battalions of the Australian 24th Infantry Brigade and the newly arrived Australian 18th Brigade (which had been detached from the 7th Division) took over the perimeter and the Australian 20th and 26th brigades took up a covering position on the outside until 9