In their illuminating book about Winston Churchill’s involvement in the discussions, planning, and logistics surrounding the Normandy landings on D-Day, Lord Richard Dannatt and Allen Packwood describe how the duties of wartime leadership took a significant toll on the British Prime Minister’s health. But as Churchill himself admitted, there was only one thing that truly filled him with fear: the German U-boats that claimed so many Allied ships during the Battle of the Atlantic. And it’s easy to see why. Britain was isolated entirely – hemmed in by Nazi-occupied Europe, with America still months away from entering the war.

The attack on Pearl Harbor on December 7, 1941, changed everything. When Japanese forces shattered the peace of that Sunday morning, Churchill knew he finally had a powerful ally in President Franklin D. Roosevelt. Roosevelt would not only commit U.S. troops against the Axis but would also put into practice the doctrine of Alfred Thayer Mahan – the naval strategist who argued that “the sea has been the element through which history’s most decisive wars have been won”, as French researcher Antony Dabila reminds us.

Roosevelt had admired Mahan’s ideas since his school days at Groton in Massachusetts. The two even exchanged letters over the years. Shortly before he died in 1914, Mahan visited the Navy Department hoping to meet Assistant Secretary Roosevelt but missed him – an anecdote that historian Phillips Payson O’Brien recounts in The Strategists (Dutton). I’ll return to that book in a future post. What matters here is the fact that Mahan left a lasting impression on Roosevelt, convincing him of the need to build a powerful navy capable of combat.

Twenty-seven years later, that lesson would bear fruit. When war erupted, Roosevelt was at the helm, ready to act. The Battle of the Atlantic had already been raging for months. Churchill’s Britain was under siege, with Royal Navy ships being hunted by U-boat wolf packs. The commander-in-chief residing on the banks of the Potomac found creative ways to support Britain, even before the U.S. officially entered the war. As James Holland writes in The Battle of the Atlantic (Penguin Random House), “Roosevelt did agree that the US Navy should now join the Battle of the Atlantic and play a part in protecting Allied shipping.”

Ironically, London’s and Washington’s greatest ally in this struggle was Hitler himself. The Nazi leader “was a continentalist and understood naval power even less than he did land warfare”—something his enemies grasped all too well. And, as Holland points out, this miscalculation ultimately cost Nazi Germany the war.

In that sense, the Allied victory in the Atlantic was also Mahan’s victory.

James Holland captures the scale and significance of this brutal, decisive campaign—one that Greyhound fans, graced by the brilliance of Tom Hanks, arguably the finest actor of our time, will especially appreciate. His work is a powerful reminder of the enduring importance of naval power throughout history—and of how it may once again prove decisive in shaping the future. The vital role played by Canada’s navy, woven throughout the narrative, stands as both a testament to past courage and a prologue to what our nation might yet achieve on the global stage in the future.

In closing Holland’s book, you come away with a more profound sense of what might have kept Churchill awake at night – and why the Battle of the Atlantic remains one of the most pivotal chapters of the Second World War.

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James Holland, The Battle of the Atlantic, London, Michael Joseph (Penguin Random House), 2018, 56 pages.

Philipps Payson O’Brien, The Strategists: Churchill, Stalin, Roosevelt, Mussolini and Hitler – How War Made Them and How They Made War, New York, Dutton, 2024, 544 pages.