'Primrose' was a British series of small-scale landings at Åndalsnes, Ålesund and Molde in central Norway in preparation for the arrival of an infantry brigade involved in the planned 'Sickle' (i) assault on Trondheim (16/19 April 1940).
The origins of the operation, which was designed to seize a clutch of small ports at which Brigadier H. de R. Morgan’s 148th Brigade would then be landed as 'Sickle' Force to close on Trondheim from the south as Brigadier C. G. Phillips’s 146th Brigade, landed as 'Maurice' Force at Namsos, closed from the north.
Although it was a port considerably smaller than Namsos, Åndalsnes possessed the advantage of offering a good axis of advance toward Trondheim, while Molde, which was about the same size as Namsos, lies some 23 miles (37 km) farther out toward the Norwegian Sea, but could be of use only be a subsidiary base because it lacked any direct road communication with Åndalsnes and the Norwegian hinterland.
An essential first step toward the occupation and use of Åndalsnes was the occupation of Ålesund, the largest port between Bergen and Trondheim, and whose island position commands the coastal route through the Inner Leads. A party of 45 officers and 680 Royal Marines and seamen under Lieutenant Colonel H. W. Simpson, Royal Marines, was drawn from three battleships then in dockyard hands and embarked in four sloops for movement to Ålesund. But while the overloaded ships were held up by a gale at Invergordon, their destination was changed, at the request of the Norwegians, to Åndalsnes, which they secured on 17 May pending the arrival of the two-battalion 148th Brigade on the following day. This brigade had been waiting since 7 April for movement to Stavanger, a destination changed on 14 April to Namsos.
The brigade was to embark at Rosyth on the light cruisers Galatea and Arethusa, and on one large transport, which lay below the Forth Bridge and therefore had to be loaded from lighters. Thus the brigade’s stores were not tactically loaded, and the brigade did not sail for another 60 hours, an interval in which new orders reached Morgan instructing him to transfer the men and as much of his stores as possible from the transport to the light anti-aircraft cruisers Carlisle and Curacao, and two destroyers, with Åndalsnes rather than Namsos now the destination.
The inevitable chaos attendant on the total of four sets of orders and the requirement to trans-ship by night meant that much equipment was left behind, this including brigade headquarters equipment (including the radio transmitter), predictors for the anti-aircraft guns, and all of one infantry battalion’s mortar ammunition. Moreover, half of one infantry battalion had to follow as a second flight for lack of accommodation in the warships.
The final orders were dated the evening of 16 April and delivered to Morgan just before the expedition sailed at 07.00 on 17 April with the light cruisers Arethusa and Galatea, light anti-aircraft cruisers Carlisle and Curacao, and two destroyers, under the command of Vice Admiral Sir George Edward-Collins.
While emphasising the fact that he would later come under command of the general officer leading the final operations for the capture of Trondheim, Morgan’s instructions laid down the 148th Brigade’s immediate tasks as landing the area of Åndalsnes, securing Dombås at the head of the Gudbrandsdalen, which provided the best axis of land access to the area for the German forces advancing to the north-west from Oslo, and operating to the north against the Germans in Trondheim area. But while he was still at sea, Morgan received a further message from Field Marshal Sir Edmund Ironside, the Chief of the Imperial General Staff, suggesting that he might be able to get to Dombås very rapidly as strong German opposition before that point was improbable, and adding another two tasks after Dombås had been secured, namely the denial to the Germans of the use of the railway to reinforce Trondheim, and the establishment of contact with the Norwegian general headquarters (believed to be in the Lillehammer area) and the prevention of the isolation of the Norwegian forces operating toward Oslo. In other words, Morgan was expected to face south as well as north.
For these expanding operations, Morgan had with him in the first flight almost exactly 1,000 men from two territorial battalions with one troop of light anti-aircraft guns. The second flight of 600 men, with all of the brigade’s motor transport and the other half of its anti-aircraft guns, was scheduled to follow two days later.
The brigade’s passage across the North Sea was shadowed by German aircraft, which made one abortive attempt to attack. To reduce the risk of air attack during the landing, about one-third of the brigade was landed at Molde, enabling disembarkation there and at Åndalsnes to be completed before the break of day on 19 April.