that month, the replacement cypher for the was broken by the Combined Bureau, Middle East (CBME). In September 1940, Wavell ordered the commanders in Sudan and Kenya to make limited attacks once the rainy season had ended. On the northern front, Platt was to attack Gallabat and the vicinity; on the southern front, Cunningham was to advance northwards from Kenya through Italian Somaliland into Ethiopia. In early November 1940, Cunningham had taken over the East African Force from Dickinson, who was in poor health. While Platt advanced from the north and Cunningham from the south, Wavell planned for a third force to be landed in British Somaliland by amphibious assault to re-take the colony, prior to advancing into Ethiopia. The three forces were to rendezvous at Addis Ababa. The conquest of the AOI would remove the land threat to supplies and reinforcements coming from Australia, New Zealand, India, South Africa and British East Africa via the Suez Canal for the Western Desert campaign and re-open the land route from Cape Town to Cairo. East Africa Force On 10 June 1940, East Africa Force (Major-General Douglas Dickinson) was established for North-East Africa, East Africa and British Central Africa. In Sudan about and guarded a frontier with the AOI. Platt had 21 companies (4,500 men) of the Sudan Defence Force (SDF) of which five (later six) were organised as motor machine-gun companies. There was no artillery, but the Sudan Horse was converting to a 3.7-inch mountain howitzer battery. The 1st Battalion Worcestershire Regiment, 1st Battalion Essex Regiment and the 2nd Battalion West Yorkshire Regiment, were, in mid-September, incorporated into the 29th Indian Infantry Brigade, 10th Indian Infantry Brigade and 9th Indian Infantry Brigade respectively of the 5th Indian Infantry Division (Major-General Lewis Heath) when it arrived. The 4th Indian Infantry Division (Major-General Noel Beresford-Peirse) was transferred from Egypt in December. The British had an assortment of armoured cars and B Squadron 4th Royal Tank Regiment (4th RTR) with Matilda infantry tanks joined the 4th Indian Division in January 1941. On the outbreak of hostilities, Lieutenant-Colonel Arthur Reginald Chater in British Somaliland had about comprising the Somaliland Camel Corps (SCC) and a battalion of the 1st Battalion Northern Rhodesia Regiment. By August, the 1/2nd Punjab and 3/5th Punjab regiments had been transferred from Aden and the 2nd Battalion of the King's African Rifles (KAR) with the 1st East African Light Battery (3.7-inch howitzers)