Royal Air Force (RAF) radar, and a ring of searchlights operated round the harbour at night. Harbour defence was by pre-arranged barrages by five of the six HAA troops, the sixth troop remaining on watch for other raiders. 4 AA Brigade recorded that there was a steady decline in numbers of aircraft attacking as the siege went on, with the attackers switching to high-level and night attacks. There was an alert for possible paratroop attack on 19 November when four Junkers Ju 52 transport aircraft flew low along the coast: one was shot down by fire from RHQ's LMGs and Shrapnel shells from 153 HAA Bty. In the last two months of the siege, troops of HAA guns took it in turn to move out to the perimeter and take on ground targets under the control of 9th Australian Division. Their long-range harassing fire made up for the shortage of medium artillery. For example, RHQ 69th HAA Rgt controlled Counter-battery shoots on 24 and 26 November. Tobruk was relieved at the end of November 1941. By then the harbour defences under 69th HAA Rgt were: 153/51 HAA Bty – 4 x 3.7-inch (mobile) 192/69 HAA Bty – 8 x 3.7-inch (mobile) 235/89 HAA Bty – 8 x 3.7-inch (static) 277/68 HAA Bty – 7 x 3.7-inch (mobile) 292/94 HAA Bty – 8 x 3.7-inch (mobile) 39/13 LAA Bty – 3 x Bofors, 9 x Breda (came under command 20 December) 40/14 LAA Bty – 12 x Bofors, 1 x twin Breda Detachment 57/14 LAA Bty – 1 x Bofors, 3 x Breda Detachment 305/27 S/L Bty – 9 x S/L (came under command 18 December) Detachment 306/27 S/L Bty – 12 x S/L Lieutenant-Colonel Ruffer, who had acted a brigade commander on occasions, was awarded the Distinguished Service Order (DSO) after the siege. Egypt After the relief, many of the AA units in Tobruk moved up in support of the advancing British Eighth Army, leaving 69th HAA Rgt at the port in command of various units passing through. In May 1942, 68th HAA Rgt HQ arrived to take over command of the AA defences. That month Rommel began a new attack into Cyrenaica. On 16 June, 69th HAA Rgt was ordered back to the Egyptian border with 192/69 and 261/94 HAA Btys, 51st HAA Rgt's signal and workshop sections, and 25th LAA Rgt's RASC transport section. It deployed at Sollum