Operations which never happened (part 2): Operation Zipper and Mailfist

In the week leading up to VE Day in 1945, British and Indian forces had succeeded in capturing the majority of Burma (modern-day Myanmar) and its capital Rangoon, without a fight, during Operations Capital and Dracula. Japanese forces had abandoned the city days before Allied forces arrived, meaning that only 24 casualties were suffered, all as a result of friendly fire.

The rapid success of these operations caused the Allied authorities to turn their attention to the swift capture of Malaya, the opening of the Straits of Malacca, and the capture of Singapore. Planners were informed on 4 May 1945 that ‘in view of the rapidly deteriorating Japanese position and the negligible Japanese naval and air threat’ it was proposed that Operation Zipper and Mailfist be launched during the second half of August to ‘accelerate the capture of Shackle’, which was the codename for Singapore (DEFE 2/648A). Records available at The National Archives reveal the scale of the planning which took place in preparation for these operations.

By the end of July 1945, planners correctly warned that with the fall of Rangoon, Japanese forces anticipated an early assault on Malaya itself and that Singapore was the ultimate objective, but were unsure as to which area was the most likely for an initial assault. They estimated that Japanese forces stood at 24 infantry battalions and 75 tanks in Malaya, a total of 59,000 troops. By the time of the commencement of Zipper, it could potentially rise to 72,000 troops. Planners called for the massing of the 5^th, 23^rd, 25^th and 26^th Indian Divisions, the 3^rd Commando Brigade and one parachute brigade of the British 6^th Airborne Division, totalling more than 100,000 troops (WO 203/4489).

These four Indian divisions had, in March 1945, been formed as the Indian XXIV Corps as part of the famous British Fourteenth Army. The latter three divisions above had all fought in the Burma campaign. The 5^th Indian Division, however, had fought during the East African campaign in 1940/1941 and was heavily involved in the Western Desert campaign and the First Battle of El Alamein, before moving to take part in the fighting in Burma. As such, it was one of very few Allied divisions which could say that it had fought against Italian, German, and Japanese forces.

Elements of the British 6^th Airborne had, of course, also landed on D-Day in June 1944, where it secured the left flank of the Allied invasion in Normandy. It had then also taken part in Operation Market Garden, the so-called ‘Bridge Too Far’, and had made its third combat air assault over the River Rhine in to Germany in March 1945.

Planning for the operation also occurred concurrently with that of Operation Downfall, the proposed invasion of mainland Japan, of which Britain wished to participate. It had been noted by British Chiefs of Staff, who had sought and obtained the approval of the United States to launch Zipper and Mailfist as long as operations did not interfere with Downfall, that the British priority would have to be the recapture of Singapore. Any British participation in the invasion of Japan, and with it the creation of a Commonwealth force, was on the condition that Malaya and Singapore were captured quickly (CAB 79/33).

The initial assault, as part of Operation Zipper, sought to secure an airfield located near Morib, and capture Port Swettenham (modern-day Port Klang), both situated near Kuala Lumpur in the middle of the western peninsula of Malaya. This was to be done by one division, while a second would immediately follow up with the object of clearing the road southwards. By D plus 3, another division, plus the Commando brigade would assault, with full naval support, the beaches south of Port Dickson, located to the south and halfway between Kuala Lumpur and Malacca.

Planners noted that a larger force than was expected had gathered in South Malaya, which they thought would slow down any advance. There was also a feeling that ‘there is now a threat of attack from suicide boats and that from suicide aircraft’. An estimation was made that between five and ten such attacks could be mounted each day. Naval vessels were in short supply, hence why the assault had to be slightly staggered, and this would ensure adequate naval air and gun support. The assault, however, was to be supported by over 500 aircraft from the Royal Air Force (DEFE 2/648A).

Once the bridgeheads had been secured, an advance south would occur by D plus 12, using one division with armour utilising the main inland and coastal roads. No firm plan had been devised for the assault and capture of Singapore. The hope was that forces could ‘jump the island’, assaulting from across the Johore Strait, with a force of two divisions, with additional support from commandos and the parachute brigade allotted to the operation. It was hoped that this element of the operation, codenamed Mailfist, could occur by December 1945.

‘D-Day’ for Operation Zipper had been pushed back to 9 September 1945 and it was, of course, cancelled as a result of the Japanese surrender in the middle of August. Instead, a version of the plan, Operation Tiderace, was launched during the first week of September, when British, Indian, Australian, and French naval forces set sail for the area. The fleet arrived in Singapore on 4 September and met no resistance. The formal surrender commenced on 12 September when Lord Louis Mountbatten, the Supreme Allied Commander of Southeast Asia Command, came to Singapore and accepted the surrender of the Japanese Southern Army Group.