In February 1940 the German tanker Altmark was making for home along the Norwegian coast, hidden in neutral waters and carrying nearly 300 British merchant seamen — prisoners taken from ships sunk by the raider Graf Spee. Finding her was the problem. RAF Coastal Command Hudsons, flying reconnaissance along the Norwegian coast, are widely credited with spotting the Altmark and helping fix her position for the Royal Navy. The destroyer HMS Cossack then cornered the ship in Jøssingfjord and boarded her, and a boarding party's shout of "The Navy's here!" became one of the war's early morale-boosting phrases. Accounts of exactly which aircraft first sighted the ship vary, so the Hudson's precise role is best stated carefully — but the type's part in the search is well established, and the episode showed how a patrol aircraft's eyes could change events at sea.

The rescue caused a diplomatic storm, since HMS Cossack had entered Norwegian territorial waters to free the prisoners, and it is sometimes cited among the events that pushed Norway toward the wider war that engulfed it weeks later. For the Hudson crews, it was an early, concrete demonstration that patient reconnaissance flying could produce results that changed the map of the war.

It is one of the strangest episodes of the war at sea. On 27 August 1941, south of Iceland, a Hudson of No. 269 Squadron caught the newly commissioned submarine U-570 on the surface. The Hudson attacked with depth charges, and the shaken, inexperienced crew — believing themselves trapped and unable to dive safely — displayed a white flag of surrender. The Hudson circled, calling in support, until surface ships could reach the scene and take the submarine in tow. It is famously remembered as the only occasion on which a U-boat effectively surrendered to an aircraft. The captured boat was taken into Royal Navy service and commissioned as HMS Graph, where Allied engineers studied her secrets. The details are dramatic enough that they are worth stating plainly and sourcing carefully, but the core of the story is firmly documented.

The capture had lasting value beyond the propaganda coup. As HMS Graph, the former U-570 was studied in detail by the Royal Navy, yielding intelligence on German submarine design and even being sent on operational patrols against her former comrades — a rare instance of a captured enemy warship turned against its builders.

Barely a month into the war, on 8 October 1939, a Hudson operating over the North Sea was involved in the destruction of a German Dornier Do 18 flying boat. The engagement is frequently described as one of the first aerial victories won by the RAF in the Second World War, and — because the Hudson was American-built — often specifically as the first enemy aircraft shot down by a US-built aeroplane in the war. As with many "firsts," the exact wording matters and sources differ on the precise claim, so it is best hedged: what is clear is that a converted American airliner drew some of the earliest Coastal Command blood of the war, a striking symbol of how quickly the Hudson had been thrown into the fight.

The engagement is usually associated with the Hudson squadrons then forming the vanguard of Coastal Command's modernisation, and it came at a moment when every early success mattered for morale. As with many wartime firsts, competing claims exist and the precise wording is disputed, but the symbolism — an American-built aircraft in RAF colours drawing early blood — was not lost on contemporaries.

For every famous action there were thousands of patrols that ended with nothing to report — and that was the point. Coastal Command's Hudsons flew long, cold, monotonous sorties over the North Sea and the Atlantic, escorting convoys and sweeping the approaches for submarines. A crew might spend six or seven hours staring at empty water, navigating by dead reckoning far from land, alert for the tell-tale feather of a periscope or the dark sliver of a surfaced U-boat. The work was exhausting and dangerous: engine failure over the sea, sudden weather, or an encounter with enemy fighters could be fatal, and rescue was far from certain. Yet this unglamorous endurance flying was decisive. By forcing U-boats to stay submerged and slow, and by escorting the convoys that kept Britain fed and armed, the Hudson and its crews helped win the long, grinding Battle of the Atlantic.

Navigation was largely a matter of dead reckoning over a featureless ocean, with a single error compounding over hundreds of miles; a lost or iced-up aircraft far from land had little margin. The men who flew these sorties rarely fired a shot, yet their vigilance underpinned everything the surface fleet and the convoys did.

One of the Hudson's most humane roles was air-sea rescue. Ditched aircrew — bomber men down in the North Sea, fighter pilots out of fuel — faced death from cold and exhaustion in the water long before a surface vessel could reach them. The answer was the airborne lifeboat: a powered, self-righting wooden boat, complete with engines, sails, food and survival gear, slung beneath a modified Hudson and dropped by parachute to men in the water. Once aboard, survivors could motor or sail toward safety rather than simply wait to be found. It was an ingenious piece of engineering carried by an aircraft whose roomy airliner airframe made such adaptations possible, and it turned many likely deaths into rescues. The airborne lifeboat became one of the quiet success stories of Coastal Command's war.

The airborne lifeboat was, famously, designed with input from the yacht designer Uffa Fox, and it turned the Hudson's roomy airframe into a genuine life-saver. Dropped accurately, it gave ditched crews shelter, propulsion and supplies — the difference between a long wait for rescue and quiet death from exposure in the North Sea.

The Hudson's range, load and reliability made it a natural choice for special-duties work: the secret flights that inserted and recovered agents of organisations such as the Special Operations Executive (SOE) into and out of German-occupied Europe. Flying low by moonlight to rough, improvised landing strips marked out by resistance workers with a handful of torches, special-duties Hudsons of squadrons such as No. 161 carried agents, radios, weapons and documents behind enemy lines and brought people back out again. It was perilous, precise flying, navigated by map and stopwatch deep into hostile territory, and it depended on an aircraft that could carry a useful load a long way and get down and up again from a farmer's field. That the same type patrolled the Atlantic by day and landed spies in France by night says much about the Hudson's versatility.

Where the tiny Lysander could land a single agent on a short strip, the larger Hudson could carry a heavier load of people and stores over a longer range, complementing the smaller aircraft on the RAF's clandestine routes into occupied Europe. The flights demanded pinpoint navigation and iron nerve, deep into hostile airspace with no margin for error.

The Royal Australian Air Force was an early and enthusiastic Hudson operator, using the type for maritime patrol across the approaches to Australia and Malaya. When Japan struck in December 1941, RAAF Hudsons were among the first Allied aircraft in action in the Pacific: Hudson crews attacked Japanese invasion convoys off Malaya and the Netherlands East Indies, and some accounts credit RAAF Hudsons with firing some of the first Commonwealth shots of the Pacific war — a claim best hedged, as such "firsts" are disputed. What is not in doubt is the ferocity of the fighting or its cost. Outnumbered and often outmatched, RAAF Hudson squadrons pressed home attacks against overwhelming Japanese air and naval strength over Malaya, Singapore, Timor and New Guinea, suffering heavy losses in the desperate defensive battles of 1941–42.

RAAF Hudson squadrons such as No. 1 and No. 8 were thrown into the Malayan campaign and suffered grievously, and individual acts of valour during those doomed weeks entered Australian air-force legend. The type went on to serve throughout the New Guinea and Timor campaigns as the tide slowly turned.

The Hudson's ancestor was a celebrity in its own right. In July 1938 the millionaire aviator Howard Hughes and a crew of four flew a Lockheed Model 14 Super Electra around the Northern Hemisphere in a little over three and a half days, shattering the record for a round-the-world flight and turning the sleek twin into front-page news. That same airliner design — fast, modern and already in production — was the basis for the Hudson. There is a neat irony in it: an aircraft built to carry passengers in comfort and to set peacetime speed records was, within months, cutting bomb bays and gun turrets into its fuselage and heading out over the North Sea to hunt submarines. The Hudson never entirely lost its airliner manners, and pilots often remarked on how civilised it felt compared with purpose-built bombers.

Hughes and his crew circled the Northern Hemisphere in a little over three and a half days in July 1938, and the record cemented the Super Electra's reputation for speed just as the British were choosing it as the basis for a bomber. The Hudson never entirely shed that airliner poise, which is partly why crews found it so pleasant to fly on long patrols.

When the United States entered the war, the Hudson was already in American service — the US Navy flew it as the PBO-1. On 1 March 1942, off Newfoundland, a PBO-1 of squadron VP-82, reportedly flown by Ensign William Tepuni, attacked and sank the submarine U-656. It is widely cited as the first German U-boat sunk by United States forces in the war, and an early demonstration that the same converted airliner giving the RAF such service could serve American crews just as well. As with several Hudson "firsts," the precise wording — first by US aircraft, first US kill of a U-boat — should be stated carefully, but the sinking itself is well documented and marks the Hudson's place at the start of America's own Battle of the Atlantic.

The victim, U-656, went down off Newfoundland on 1 March 1942, and the action announced that the United States, too, would fight the U-boats from the air. That the aircraft responsible was a Hudson — already a veteran of British service — underlined how thoroughly the type had become an Allied common denominator.

The Royal New Zealand Air Force operated Hudsons heavily in the South Pacific, where the type's range and endurance suited the vast distances between island bases. RNZAF Hudson squadrons flew maritime reconnaissance, convoy escort and bombing missions in the campaigns across the Solomon Islands and the surrounding seas, searching for Japanese shipping and supporting Allied operations as the tide of the Pacific war slowly turned. For a small air force fighting across an ocean, the Hudson was a workhorse: available, reliable and adaptable, filling patrol and strike roles until more specialised aircraft arrived. New Zealand's Hudson crews shared the same grinding, dangerous over-water flying as their Coastal Command counterparts half a world away, only under a tropical sun rather than a North Sea sky.

RNZAF Hudsons operated in support of the long campaign in the Solomon Islands, flying reconnaissance and strike missions across seas contested by the Japanese. For a small nation fighting across vast Pacific distances, the type's endurance and reliability made it a genuine workhorse until more specialised aircraft arrived.

Canada was a major Hudson operator, using the type for anti-submarine patrol and reconnaissance over the western Atlantic approaches, where U-boats hunted the convoys forming up off Halifax and Newfoundland. The Hudson also played a part in one of the war's logistical breakthroughs: the ferrying of American-built aircraft across the Atlantic by air rather than by ship. Beginning in 1940, Hudsons were among the types flown across the ocean from Newfoundland to Britain, proving that mass transatlantic delivery flights were possible and helping to establish the ferry organisation that would move thousands of aircraft to the war. For the Royal Canadian Air Force, the Hudson was both a patrol aircraft guarding the sea lanes and a pioneer of the air bridge that helped keep Britain supplied.

From late 1940, Hudsons were among the first aircraft flown across the Atlantic in the pioneering ferry flights from Newfoundland to Britain, proving that mass delivery by air was possible. The organisation that grew from those flights would move thousands of aircraft to the war, and the Hudson helped show the way.

The military air arm of the Netherlands East Indies operated Hudsons in the doomed defence of the archipelago against the Japanese onslaught of early 1942. Alongside Australian, British and American units, Dutch Hudson crews attacked Japanese invasion fleets and airfields across the East Indies, flying against odds that grew more hopeless by the week as island after island fell. Many were lost; some surviving aircraft and crews escaped to Australia to fight on. The Hudson's service with the Netherlands, China and Brazil is a reminder of just how widely the type was spread among the Allied and associated air forces — an American airliner-turned-bomber that ended up flying in the colours of a remarkable number of nations. Precise Dutch fleet numbers are uncertain and should be treated as approximate.

Flying alongside Australian, British and American units, the air arm of the Netherlands East Indies pressed its Hudsons against the Japanese onslaught until resistance collapsed; some surviving crews and aircraft escaped to Australia to fight on. Precise Dutch numbers are uncertain and should be treated as approximate.