Personnel and equipment began to assemble at Royal Naval Air Station Ludham in Norfolk, the headquarters of the Mobile Naval Airfields Organisation (MNAO), on the 15th November 1944. The unit was to form as a type A MONAB, to support up to 100 a/c comprising of resident and disembarked squadrons. It was to be a crowed time at Ludham, the timetable for the formation and despatch of units was tight, and at any given time there were three units in residence at varying stages of formation. MONAB IV was timetabled to begin assembly on the 15th November; MONABs I & II departing by road and rail for Liverpool docks during the 18th –20th.

MONAB III was a month into its formation period, having begun assembling on the 18th October, and would commission as HMS Nabstock on the 4th December 1944. On the same day personnel for the administration elements of Transportable Aircraft Maintenance Yard No. 1 (TAMY 1) began to assemble at Ludham. MONAB III had departed by the 22nd December, they were soon to be replaced, the personnel for MONAB V began to assemble on the 28th.

The severe winter of 1944 was to compound the strain of the day-to-day routines of the assembling units, things inevitably slowed down; ratings were forced to queue for hours in rain, mud and snow for personal kit issues. Ludham was not an ideal base for the formation of units like MONABs; it was a dispersed airfield where all of the facilities were located around the outer edges of the base. The majority of the airfield was open grass, this was used for all manner of purposes from vehicle parks to large areas of tented accommodation erected to house the personnel of the assembling MONAB units; all became a quagmire.

MONAB IV was to comprise of Mobile Maintenance unit No. 3 (MM 3), Maintenance Servicing units No. 5 & 6, Maintenance Annex No. 1 (M.A. 1), and was to provide support facilities fort he following aircraft types:

M.A. 1 Aircraft type not known
M.M. 3 Avenger I & II, Firefly I, Seafire III & L.III
M.S. 5 Corsair II & IV
M.S. 6 Hellcat I & II

Components added after arrival in the Pacific theatre in response to a change in roles: Maintenance, Storage & Reserve (M.S.R.) units 1, 4, 6. Mobile Air Torpedo Maintenance Unit (M.A.T.M.U.) No. 7

M.S.R. 1* Avenger I & II, Corsair II & IV, Hellcat I & II.
M.S.R. 4 Avenger I & II, Corsair II & IV, Hellcat I & II
M.S.R. 6 Firefly I, Seafire III & L.III, Sea Otter

* Formed the forward Aircraft Pool (F.A.P.) on Pityilu Island under MONAB 4 control.

Mobile Operational Naval Air Base No. 4 commissioned on New Year’s day 1945 at Ludham, as an independent command bearing the ship's name 'HMS NABARON', Captain A.N.C. BINGLEY in command.

On the 16th January 1945 the unit’s personnel, Stores and equipment were transported to Liverpool for embarkation.  The personnel embarked in the SS. Dominion Monarch, stores and equipment in the S.S. Clan Macauley. The S.S. Dominian Monarch arrived at Sydney, Australia on the 21st February, the personnel disembarking to Warwick Farm Race Course, HMS Golden Hind, to await the allocation of an operating base.

Departmental officers lived in Sydney and were thus able to liase directly with the staff of the Flag Officer Naval Air Stations (Australia) . This was a most helpful exercise, which resulted in the unit acquiring some domestic refrigerators and "Wiles Mobile Galleys" to replace the antiquated and unsuitable types provided in U.K. As it transpired no mobile galleys were actually needed, however the the Wiles Mobile Galley was considered to be ideal for a forward operating MONAB.

The planning staff of the BPF headquarters decided that MONAB IV would become the first unit to be established in the forward area, its operational base was to be at Ponam, in the Admiralty Islands, where USN airfield facilities had been loaned from the Americans. To this end the SS. Clan Macaully, still en route, was diverted to the fleet anchorage at Manus, Admiralty Islands in preparation for occupying Ponam airfield.  This decision meant that in addition to its primary role of supporting disembarked front line squadrons, MONAB IV was also tasked with providing reserve aircraft storage. Reserve airframes would be issued to the fleet as required or ferried forward in replenishment carriers to provide replenishments at sea as part of the Fleet Train, the support ships of the BPF.

In order o provide the storage facility an additional component was added to the units compliment, Maintenance Storage & Repair unit no. 4 (M.S.R. 4) which transferred from the strength of MONAB II (RNAS Bankstown, Sydney) disembarking to USN airstrip Ponam from HMS Unicorn in late February to await the arrival of the advance party of HMS Nabaron.