Invading Iceland
By Mike Bennighof, Ph.D.
December 2022

Sitting roughly in the middle of the North Atlantic, Iceland is a large volcanic island with a sparse population and few natural resources. After a brief and disastrous fling as a nation of amateur banking moguls, Icelanders once again make their living from the sea for the most part, relying on their island for its natural beauty and cheap geothermal heating. In 1941, the population numbered only 120,000. Strategically, Iceland can provide bases within easy striking distance of the North Atlantic trade routes.

Though Icelanders point to a democratic tradition over a thousand years old, the island has only been formally independent since 1944. From its settlement by Vikings in the 9th century, Icelanders swore fealty and occasionally paid taxes to the kings of Norway. In 1814, their very nominal fealty passed to the King of Denmark.

Iceland entered World War II involuntarily. Germany had its “Fall Ikarus” and the United States its “War Plan Indigo” to seize the island, but it was Britain that moved first. Denmark yielded to German occupation in April, 1940, without putting up organized resistance. On 10 May 1940, a battalion of Royal Marines invaded and seized Iceland’s capital of Reykjavik. Over the next few months, British and Canadian reinforcements swelled the occupation force to 25,000 men.

Uneasy with their uninvited guests, but even more unwilling to see Germans land on their island, the Icelanders looked for ways to have it both ways. A tiny pro-Nazi movement did exist, but feelings ran mostly toward keeping any foreign troops off the island. In December, 1940, the Icelanders began unofficial talks with the United States to declare Iceland part of the Western Hemisphere and send American troops to replace the British garrison.

As 1941 dragged on, the British Army sought to use its troops elsewhere, and formally asked for an American commitment. President Franklin D. Roosevelt agreed, provided that Iceland made the request. The Icelanders, already touchy about their future being decided without them, balked at doing Winston Churchill’s bidding. Only under extreme British pressure did the Icelanders finally invite the Americans, and only once the Americans were already on their way at that.

Roosevelt had limited forces at his disposal. The first suggestion by the War Department had been to send either the 1st or the 5th Infantry Division, as the nucleus of a total force of about 30,000. By the law of those days, obviously amended since, draftees and National Guardsmen could not be sent outside the Western Hemisphere unless they volunteered specifically for the duty. The Army’s massive expansion had integrated huge numbers of draftees into every large unit. Army generals believed, probably correctly, that they could not withdraw long-service regulars from their new units without crippling the divisional training programs.

This left Roosevelt with Marines as his only choice. All Marines, both regulars and reservists, were volunteers with no limits on their deployment even in peacetime. On 5 June 1941, the president ordered a Marine brigade made ready to sail for Iceland within 15 days. Initial plans, later cancelled, called for the 5th Infantry Division to follow as soon as draftees could be replaced by regulars and volunteers gathered from other units.

War Plan Indigo

Marine planners had already received orders to prepare a brigade for a completely different operation. War Plan Gray posited the American occupation of the Azores, an operation Roosevelt had already approved. Like the Army, the Marine Corps had begun a large-scale expansion. The Corps planned to mobilize two divisions, the 1st on the East Coast and 2nd on the West. The 6th Marine Regiment was already on its way from San Diego to Camp Lejeune to reinforce the 1st Marine Division for its landing in the Azores. Riflemen from the 2nd and 8th Marines had been added to bring the 6th to full strength, along with some tank, artillery and engineer elements.

Well-dressed U.S. Marines on a field exercise in Iceland.

Roosevelt ordered the move into the Portuguese-ruled Atlantic islands placed on hold and the troops diverted northward to War Plan Indigo, the occupation of Iceland. From the 1st Marine Division, the 2nd Battalion of the 10th Marines (an artillery unit with three batteries of 75mm pack howitzers) also joined the brigade. The 1st Division also provided more support units, and the 5th Marine Defense Battalion from Parris Island was added to provide anti-aircraft support. All of these units headed for Charleston, South Carolina to form a convoy. Marine Brigadier General John Marston received the command and a blunt set of orders: “Defend Iceland Against Hostile Attack.”

Marston had commanded the Marine contingent in North China and seemed destined for greater things. He led 2nd Marine Division to the South Pacific in 1942, but was replaced by A.A. Vandegrift just before the Guadalcanal landings and promoted to command the Marine establishment in the Pacific Theater.

The convoy, escorted by the battleships Arkansas and New York, left Charleston on 22 June. The troopships arrived at Reykjavik on 7 July. While the transports off-loaded the heavy equipment at the harbor’s lone quay the Marines hit the beach from Higgins boats. Though formally separate from the British command on the island, Marston accepted a sector assignment from the British 49th Division’s commander, Major General Henry O. Curtis, and moved his men into position behind the stony beaches just south of Reykjavik. Most Marines would form a mobile reaction force to meet any German landing. British trucks moved Marine gear and British kitchens fed the men while their own gear was being unloaded. Curtis himself became popular with the Marines when they discovered that he was one of the few Britons to actually understand and play baseball.

In September, the brigade came under U.S. Army command on “detached service,” as Army units slowly began to filter into the theater. The Pearl Harbor attack brought strident Navy demands for the brigade’s return, but delays in arranging shipping only brought the Marines back to New York in March. The units returned to their divisions, and most of the Iceland Marines fought in the South Pacific.

Fall Ikarus

Germany also recognized Iceland’s strategic significance. If the island could somehow be seized, air units based there could wreak havoc on the shipping lanes between Britain and the Western Hemisphere. Naval forces, especially submarines, could also sortie from the island to attack convoy routes.

Getting there would be the problem. The Kriegsmarine had pulled off an extraordinary feat by seizing Norway in the teeth of British naval supremacy. Even then, the German fleet lost many valuable warships. But Fall Weserübung, the invasion of Norway, took place with considerable Air Force assistance. Other than a few long-range reconnaissance squadrons, any air units sent to Iceland would require naval transport to get there. And their entire ground echelon, plus fuel and other supplies, would have to come by ship as well.

Despite these difficulties, the German Navy put together a plan called Fall Ikarus. The planning staff concluded that the operation itself would be feasible, especially if executed late in the year (with long nights to help cover naval movements). However, it saw little advantage to the move. Since re-supply convoys would be difficult if not impossible to bring through to the island, the British would eventually re-capture Iceland and any troops sent there would be lost.

Liners Europa (left) and Bremen seen at Bremerhaven in 1930.

Overruling this seemingly crucial objection, Hitler ordered the navy to begin long-term preparations to execute the operation. In this plan, a provisional brigade of mountain troops drawn from the 3rd Mountain Division then stationed in northern Norway would make a quick dash to Reykjavik. The big liners Bremen and Europa had already begun a rapid refit for use as fast troop transports for Operation Naumburg, the reinforcement of 3rd Mountain Division by sea during the struggle for Narvik in the spring of 1940. They had even been fitted to bring a dozen tanks each and unload them by lighter, and these would be available for Ikarus as well.

The two liners would carry the brigade, which would be short of heavy weapons. The jägers would secure the harbor at Reykjavik and that at Hvalfjord nearby, defeating any British forces they found. Whatever heavy warships then available would escort the liners, but the battleships or cruisers would only remain briefly to provide a quick bombardment – the German Navy had no protocol for actual coordinated fire support. Ikarus would depend on surprise and speed.

At the core of the Ikarus force (which apparently never received a designation) would be the 139th Mountain Regiment. The division would add bicycle, engineer and pack artillery elements as well, with a tank company drawn from the 40th Tank Battalion to round out the force. Thus the German brigade would be very similar in strength to the American marine brigade that might have awaited it.

Germany’s sneak attack on the Soviet Union in June 1941 – launched on the same day the American Marines arrived in Iceland – brought an end to the unwieldy plan. German attacks on Atlantic convoys would have to depend on bases in Norway and France instead, and Iceland avoided the devastation of ground combat.

Click here to order Second World War at Sea: Plan Z (book edition) right now.

Sign up for our newsletter right here. Your info will never be sold or transferred; we'll just use it to update you on new games and new offers.

Mike Bennighof is president of Avalanche Press and holds a doctorate in history from Emory University. A Fulbright Scholar and NASA Journalist in Space finalist, he has published a great many books, games and articles on historical subjects; people are saying that some of them are actually good. He lives in Birmingham, Alabama with his wife, three children and his new puppy. He will never forget his dog, Leopold. Leopold was an unplanned dog.

Want to keep Daily Content free of third-party ads? You can send us some love (and cash) through this link right here.