“Atlantic campaign truly constituted the war’s premier maritime struggle and the true finest hour in Britain’s long and illustrious military history.”

By Brian E. Walter

BRITAIN’S LONG AND celebrated maritime history is studded with epic triumphs. The defeat of the Spanish Armada, the battles of Cape St. Vincent, the Nile and Trafalgar all loom large as defining moments in the annals of British sea power. But perhaps the Royal Navy’s greatest victory of all was the Battle of the Atlantic (1939 to 1945). This was a colossal contest waged against a powerful adversary across an ocean spanning two hemispheres. In many respects, this gruelling slog might seem an unlikely candidate to be Britain’s foremost maritime contest as it included no major fleet actions. Yet in terms of its size, duration and relevance, the Atlantic campaign was the Second World War’s premier maritime struggle and arguably Britain’s greatest military triumph.  At stake was not only the survival of the British nation, but the future of the free world itself.

To understand its relevance, it’s necessary to place the naval conflict in the context of the wider war. Despite its global reach, World War Two was essentially a contest between six major powers divided evenly into two competing camps: the British Commonwealth of Nations, the Soviet Union and the United States for the Allies and Nazi Germany, the Kingdom of Italy and the Japanese Empire for the Axis. Observers at the time and subsequent historians have substantially agreed that Germany was the greatest threat, and all three of the major Allied powers expended the bulk of their resources on defeating Germany and winning the war in Europe.

For the Western Allies (Britain and the United States), this undertaking manifested itself into five major campaigns (maritime, African, Southern European, strategic bombing and Northwest European). While each of these enterprises contributed significantly to the Allied victory in Europe, the most important component was the maritime campaign. Indeed, none of the other campaigns would have been possible without success at sea.  Effective use of seaborne lines of communication provided an essential catalyst for the entire Allied war effort, and it was only through this success that Britain was able to survive and the United States was able to bring its massive human and materiel resources to bear in the European conflict. Without victory at sea, there would have been no Western alliance, and the Soviet Union would have faced the full brunt of the German war machine alone.

In waging this campaign, the British assigned four major strategic roles to its maritime forces. These were to deter invasion, secure vital seaborne lines of communication, impose a maritime blockade against Germany and support the needs of the army. In each of these efforts, the British were substantially successful. In terms of deterring invasion, it was the strength of the Royal Navy and Britain’s demonstrated willingness to exercise this power that provided the greatest impediment to Germany’s invasion plans in the summer and autumn of 1940. Early that same year, the successful seaborne evacuation of the British Expeditionary Force from France provided a major impetus in Britain’s decision to fight on.

Once Britain’s immediate survival was secured, it was only through the preservation of the shipping lanes that the nation’s continuing participation in the war was sustained. Although primarily centred in the North Atlantic, where the battle derived its popular name, this struggle actually spanned all the world’s oceans and ran for a period of almost six years. During this time, the British successfully defended their seaborne commerce against a myriad of threats, including Germany’s vaunted U-boat arm, thus securing Britain’s national survival and facilitating effective combat operations in a number of disparate theatres including the Far East, the Middle East, Southern Europe and eventually Northwest Europe.

Accompanying this campaign was a concurrent British effort to blockade Germany and deprive it of all forms of maritime commerce. Although often overshadowed by Britain’s other naval efforts, this offensive against German shipping ran just as long and encompassed numerous operations across the entire globe, with particular emphasis placed in the waters off Northwest Europe and the Baltic. Through the use of a variety of weapons including aerial and ship-laid mines, maritime strike aircraft, bombers, submarines and surface warships, the British and Allies eventually destroyed some 80 percent of Germany’s accumulated merchant fleet, reduced its seaborne imports to a trickle, and forced Berlin to divert substantial resources to defend against this onslaught.

Finally, the British used its vast maritime power to provide vital support for the army. This assistance manifested itself in many ways including the provision of maritime supplies, the successful execution of amphibious landings, the carrying out of innumerable shore bombardments in support of ground forces, the interdiction of Axis logistical efforts and the timely execution of seaborne evacuations and rescues when fortunes faltered on the battlefield. The pinnacle of this effort was the Normandy invasion where 79 percent of the warships and over 60 percent of the landing vessels involved in D-Day came from British or Commonwealth navies.

Beyond these direct contributions, the British war at sea forced Germany to divert a substantial amount of its finite resources into countering the maritime threat. Unlike the conventional view that Germany waged a two-front war, the Western Allies actually forced Germany into a five-front contest (eastern, western, southern, aerial and maritime).  Although not normally viewed as a major naval power, Germany actually accumulated more principle warships than did the Imperial Japanese Navy. While roughly three-quarters of these were U-boats, it also fielded 450 surface warships ranging from battleships to fleet minesweepers.

The Royal Navy was the dominant player in this maritime contest. It was Great Britain that provided the majority of resources, conducted the majority of operations, suffered the majority of losses and scored the majority of successes against the German navy and merchant fleet. For its part, Britain inflicted or contributed to 100 percent of Germany’s capital ship losses, 75 percent of the total enemy cruisers destroyed, as well as 80 percent of destroyers and torpedo boats. Furthermore, 77 percent of U-boats lost were destroyed by British forces and 73 percent of Germany’s merchant vessels were sunk by Royal Navy vessels, Fleet Air Arm and RAF aircraft or British-laid mines. These successes helped foster an attrition rate of 4.8 Axis warships destroyed for every corresponding British loss. Given these results and the stakes involved, the Atlantic campaign truly constituted the war’s premier maritime struggle and the true finest hour in Britain’s long and illustrious military history.

Brian E. Walter is the author of The Longest Campaign: Britain’s Maritime Struggle in the Atlantic and Northwest Europe, 1939–1945. A retired army officer from a combat arms branch, he had a Bachelor of Science Degree in Political Science and International Relations. A Distinguished Military Graduate and recipient of the Excellence in Military History Award from the U.S. Army Center for Military History and the Association of the United States Army, he has been a student of the British military during the Second World War for more than 30 years. He currently resides in his home state of Minnesota in the United States where he continues to write on a number of military and historical subjects.