'Cirrhus' was the British reoccupation of the northern part of the island of Sumatra after the surrender of the occupying Japanese forces (summer/autumn 1945).

On 4 October a convoy carrying the headquarters of Major General H. M. Chambers’s Indian 26^th Division, Captain G. B. Sayer (the naval force commander), the headquarters of Brigadier H. P. L. Hutchinson’s Indian 71^st Brigade, the headquarters of Brigadier T. E. D. Kelly’s Royal Artillery Indian 26^th Division, 1/Lincolnshire Regiment, 6/South Wales Borderers, 1/18^th Royal Garhwal Rifles and large numbers of support troops departed Madras for Sumatra. At sea the convoy split, the headquarters of the naval force, the Indian 26^th Division, the Indian 71^st Brigade, the Lincolns and the Garhwals making for Padang, half-way down the south-western coast of Sumatra, while the headquarters of the Royal Artillery and the South Wales Borderers made for Medan on the north-eastern coast.

Each part of the convoy had five tank landing ships, some of which joined en route from Malaya, Colombo and Chittagong.

The second lift of Allied troops to Sumatra began on 29 October with the arrival at Medan from Madras of the 6/6^th Rajputana Rifles (less one company already at Padang with headquarters of the Indian 26^th Division) together with one company of the 2^nd Patiala Infantry, followed during the next few days by Brigadier J. F. R. Forman’s Indian 4^th Brigade, comprising the 2/7^th Rajput, 8/8^th Punjab and 2/13^th Frontier Force Rifles. The 8/8^th Punjab moved across Sumatra by road without incident to join the Indian 71^st Brigade at Padang, and 6/South Wales Borderers replaced it in the Indian 4^th Brigade. The forces in the area of Medan were then reorganised: the headquarters of the Royal Artillery Indian 26^th Division, with the Rajputs under command, became Headquarters Medan Area responsible for the security of the town and port, while the Indian 4^th Brigade was given the task of providing a striking force for operations anywhere in northern Sumatra, including keeping open the road from Medan to Fort de Kock.

During November and December the Indian 4^th Brigade was reinforced by the armoured cars of A Squadron 146^th Regiment Royal Armoured Corps, and the Headquarters Medan Area by the 12^th Frontier Force Machine Gun Battalion, Indian 7^th Field Artillery Regiment and 2^nd Patiala Infantry.