A Tale of Two Invasions

Most people recognize 6 June 1944 as D-Day, when Americans, British, and Canadians, with assistance from the forces of 17 other nations, assaulted northern France in Operation Neptune, the initial phase of the invasion of Normandy, Operation Overlord. Fewer people remember that June 1944 had another D-Day, when on the 15th, the United States conducted a massive amphibious landing on the Japanese-held Mariana Islands. Known as Operation Forager, this D-Day equaled Neptune in some respects and exceeded it in others.

The nature and geography of the objectives, the threats faced, and even the political environment presented each landing with surprisingly different challenges that are interesting to contrast; in fact, the biggest thing the two operations had in common was their immense size. As historian Samuel Morison wrote, “Added together, ‘Neptune’ in Europe and ‘Forager’ in the Pacific made the greatest military effort ever put forth by the United States or any other nation at one time.”¹ 

Scale of Effort 

Forager’s initial lift was four and a half divisions, of which two landed on Saipan. Fierce resistance and the approach of the Japanese fleet delayed a second landing scheduled for Guam on 18 June. Five Allied divisions initially came ashore over the beaches of Normandy (with three more through the air). 

The Allies flew 14,674 bomber, fighter, transport, and reconnaissance sorties on 6 June. Over Saipan on 15 June, each of the eight escort carriers present flew roughly 70 sorties, including combat air patrol, while two of the fast carrier groups, 58.2 and 58.3, contributed 665 sorties, for a total of slightly more than 1,200 sorties.² 

Including everything from battleships to midget submarines, from attack transports to landing barges, Operation Neptune deployed 5,339 hulls, while Forager had just over 1,000. But comparing gross numbers can be misleading.

Forager deployed more capital ships and large amphibious units. In terms of minor combatants, support vessels, and, most important, men and aircraft, Neptune was much the greater operation. 

Nature of the Objective

Neptune’s objective was the invasion of a continent; Forager’s was the occupation of an archipelago. Preparations to invade France had their embryonic beginnings in 1940. The decision to invade the Marianas was made in January 1944, and serious planning did not start until mid-March. Both operations accepted a high level of risk, but the stakes in Normandy were much greater. As General Alan Brooke, Chief of the British Imperial General Staff, wrote in his diary on 5 June 1944, “At the worst it may well be the most ghastly disaster of the whole war.” Brooke confessed that Neptune was “eating into my heart.”³

On the other hand, defeat in the Marianas would have delayed the U.S. offensive against Japan but the strategic consequences were greater for the Japanese Empire than for the United States.

Amphibious Arts Experience

The vast majority of the Navy and Marine forces deployed for Operation Forager were well-trained and well-practiced in the difficult art of amphibious warfare. The chain of command started with Admiral Chester Nimitz, commander of the Pacific Fleet since early 1942. His headquarters had overseen major amphibious operations from Guadalcanal in August 1942 through the Marshalls in February 1944. Fifth Fleet commander Admiral Raymond A. Spruance had commanded naval forces supporting amphibious operations against the Gilberts and Marshalls. Vice Admiral Richmond K. Turner, commander of Forager’s joint expeditionary force, had led four major amphibious operations before undertaking Forager. When it came to actual experience in amphibious warfare, the Pacific Fleet’s V Amphibious Corps was, from top to bottom, unmatched.

For Operation Neptune, the institutional level of experience was high. The headquarters of General Dwight D. Eisenhower, which oversaw the operation’s planning, had orchestrated the invasions of North Africa and Sicily. British Admiral Bertram Ramsay was in overall command of the naval forces, with U.S. Rear Admiral Alan G. Kirk heading the Western Task Force and British Rear Admiral Philip Vian the Eastern Task Force. 

Kirk had served in the invasion of Sicily, Operation Husky. Vian had commanded warship divisions, including the escort carriers at the Salerno, Italy, landings—Operation Avalanche—but Neptune was his first amphibious command. Ramsay had done much of the planning for Operation Torch, the invasion of Vichy French North Africa, and had commanded the British Eastern Task Force in Husky. Some of Neptune’s transport and warship captains and commanders had participated in Torch, Husky, or Avalanche, but many more were serving in their first major amphibious operation, and the majority of the units and ships involved were experiencing their first taste of amphibious warfare. 

Threats

The most dangerous threats to the landing forces in Normandy would materialize during the post-amphibious stage. The Allies’ challenge was not just to establish a beachhead, but also to rush troops and supplies ashore faster than Germany could reinforce the front by road and rail. German submarines, destroyers, and motor torpedo boats sortied against the Allied naval colossus for several nights after the landing, but managed only to sink a destroyer and a pair of landing ships. The Allied naval defenses were just too vast for the Germans seriously to threaten the landings by sea. 

In the case of Forager, the threats were exactly the opposite. Japanese troops on Saipan had no possibility of reinforcement. Once the Americans were ashore and assured of supply, the Japanese were doomed. In this case, the Japanese Navy was the greater threat. The Combined Fleet sortied with a force of aircraft carriers and battleships, and had it been able to attack the amphibious force, the invasion could have been defeated. To defend against this threat, fleet carriers and fast battleships screened Forager instead of destroyer escorts and submarine chasers. A fleet action was indeed fought, and at the Battle of the Philippine Sea, the U.S. Navy defeated the Combined Fleet. 

Off Normandy, on the other hand, the largest naval action was between destroyer flotillas. Antisubmarine hunter-killer groups operating beyond the English Channel eliminated the threat from U-boats. 

Combined and Joint

Forager was an all-U.S. affair: Every ship, every infantryman, every aircraft was American. During Neptune, British, U.S., Canadian, and a few French troops came ashore in the initial landings, and ships from the navies of the United Kingdom, the United States, Canada, France, Poland, the Netherlands, Norway, and Greece were involved. Over the course of the campaign, 20 nations contributed in some way to the action. As well as being a combined (multinational) operation, Neptune was a joint operation in that different service branches—navy, army, and air force—were all major players and sought to apply their different priorities and ways of conducting war to the operation. 

Add to this the fact that the world’s attention was focused on Neptune. Politicians and the public scrutinized every action and decision made by the commanders tasked with invading France. A quote from Eisenhower’s diary distills the tension such high-profile multinational, multiservice operations conducted under political scrutiny engender. The Royal Air Force’s Chief of Air Staff (CAS) had agreed that the different air commands involved in Neptune were to take orders from Eisenhower. But, on 12 April, the general complained: “[I]t now develops that our plan for bombarding certain transportation centers may involve such a loss of French life that the British cabinet is objecting to part of the plan. . . . [T]his prevents the CAS from placing the two bomber forces under my command. I protested bitterly at allowing details of a few targets to interfere with the operation of a whole plan.”⁴

The admirals commanding Forager operated in a much different environment. The U.S. Navy supplied all the ships, most of the troops (Marines), and nearly all the air power. Nimitz did not have the world’s attention focused on the operation and could concentrate on its military aspects. The nearest politicians that mattered were half a world away, and they were fixated on Normandy. 

Geography and Weather

Normandy was roughly a hundred miles from Portsmouth. The infrastructure of England was completely at the disposal of the Allies. Since a cross-Channel operation had been on the books as a major invasion since April 1942, the Allies literally had years to build the airfields, ports, roads, and support apparatus required. 

The situation for Forager was the polar opposite. Saipan was 1,017 miles from Eniwetok, the nearest Allied anchorage, and 3,500 miles from Pearl Harbor, the closest major base. The landing force had to bring everything needed because there was no quick resupply. There were no nearby bases for air support. The wounded had to be treated on site. In the event of disaster, there was no place to retreat. 

All military operations are subject to the vagaries of the weather. The English Channel was especially problematic. In fact, poor weather caused Neptune to be delayed for a day, and on 19 June, an unprecedented storm—the “Great Gale of 19–21 June” destroyed one artificial Mulberry harbor and inflicted more damage on the Allied infrastructure than had the Germans.

The weather in the Marianas, on the other hand, was tropical. June was the end of the relatively cooler dry season. Nonetheless, weather affected Forager. One of the amphibious commanders noted that on D-Day “a heavy swell . . . prevented delivery of supplies across the barrier reef facing Red, Green, and Yellow beaches” and forced all supplies for the entire landing to be delivered across a single beach. The possibility of a typhoon blowing up was always in the background.⁵ 

Two Great Invasions

Neptune and Forager were difficult and daring operations. Without question, Neptune was the more crucial operation and deservedly gets the most attention. But only such a massive, long-anticipated, and important event could overshadow Forager. The size of the forces the United States was able to deploy, and the distances they had to travel, boggle the mind. 

It is fascinating to wonder how the course of the war in Europe would have gone had a significant portion of the assets used in Forager instead been applied in France, especially if it had been applied earlier. Nonetheless, the size and scope of the amphibious operations conducted in June 1944 makes that month one of the most important and interesting periods in amphibious warfare history.