response to appeals for assistance from Britain, the new Prime Minister of South Africa, Jan Smuts, sent the 1st Infantry Brigade Group to Kenya in July, followed by the South African 1st Infantry Division in November. When Robertson arrived in Nairobi, he joined the staff of Major-General D. P. Dickinson's East Africa Force as its Assistant Quartermaster General (AQMG), working under the Deputy Quartermaster General (DQMG), Colonel Alan Duff. The Kenya and Uganda Railway had ample capacity to move supplies from the base depots as far as Thika and Nanyuki; but these railheads were a long way from the frontier. There were two roads: one from Thika to Garissa and thence to Kismayu in Somalia; and one from Nanyuki to Wajir, and thence to Bardera in Somalia. They were passable only by light vehicles in dry weather, but work commenced on improving them when the war began. Forward supply bases were established at Bura and Garissa. The dominant problem was the supply of water; at the bases it was obtained from the Tana River, but forward of that it was scarce, and water obtained by boring was brackish. When not at headquarters, Robertson sited dumps, arranged for water supplies, and investigated delays at the railhead at Thika. In view of these difficulties, Lieutenant-General Alan Cunningham, who assumed command of East Africa Force on 1 November 1940, postponed operations until after the spring rains. However, the success of Lieutenant-General Richard O'Connor's operation in the Libyan Desert and Lieutenant-General William Platt's in Eritrea convinced him that the operation could be attempted with fewer troops than he originally contemplated, and the campaign began on 11 February 1941. Kismayu was occupied on 14 February, opening up a sea line of communications to replace the road from Thika. This was followed by the capture of Mogadishu on 23 February, but its development as a port was delayed because the Royal Navy had sown the harbour with magnetic mines, which it lacked the ability to clear. The small port of Merca was therefore developed as a temporary base until Mogadishu was opened in March. The offer of rewards to local civilians for the disclosure of the whereabouts of fuel supplies yielded of petrol and of aviation spirit. There was no respite for Duff and Robertson to accumulate supplies, as Cunningham decided to press on to Addis Ababa. To support this, a new line of communications was