Since the end of the 15th century, Western explorers (European exploration) have attempted to establish a commercial (international trade) sea route north and west around the American land barrier encountered by Christopher Columbus. Such an accomplishment would realize an objective that has eluded man since King Henry VII of England sent John Cabot in search of a northwest route to the Orient in 1497. Five years earlier, Columbus had set out in search of a westward route after conquest of the Middle East by the Ottoman Turks in the mid-15th century disrupted Europe's overland routes to the East. Vasco da Gama sailed south around Africa to India in 1498; Ferdinand Magellan sailed southwest around South America to the East Indies in 1521; and Dutch explorers vainly sought a northeast passage around Russia. But it was the Northwest Passage that captured the imagination of many of the world's famed explorers, including Jacques Cartier, Sir Francis Drake, Sir Martin Frobisher, and Captain James Cook. All met with failure, and many with disaster. Sir Humphrey Gilbert (Gilbert, Sir Humphrey), whose treatise on the passage inspired many voyages by others, drowned on his own attempt in 1583. Henry Hudson (Hudson, Henry), his young son, and seven others were cast adrift by a mutinous crew in 1611, when his discovery of Hudson Bay proved to be an icy trap instead of the passage he sought. Knowledge of an Arctic passage came slowly, over hundreds of years, from information gathered during voyages by such explorers as John Davis, William Baffin, Sir John Ross, Sir William Parry, Frederick William Beechey, and Sir George Back, augmented by overland expeditions by Henry Kelsey, Samuel Hearne, and Sir Alexander Mackenzie. The worst tragedy came when Sir John Franklin (Franklin, Sir John) and 128 men aboard HMS Erebus and HMS Terror vanished in 1845. One searcher for the lost expedition, Robert McClure (McClure, Sir Robert John Le Mesurier), entered the passage from the west, became locked in the ice for two winters, then sledged overland to another rescue ship coming from the east to complete the first Northwest Passage in 1854. Adolf Erik Nordenskiöld led a Swedish-Russian voyage through the Northeast Passage over the top of Eurasia in 1878–79, and Soviet polar icebreakers have opened this route to limited use in modern times. But the Northwest Passage was not finally conquered by sea until 1906, when the Norwegian explorer Roald Amundsen (Amundsen, Roald), who had sailed secretly to escape creditors seeking to stop the expedition, completed an arduous three-year voyage in the converted 47-ton herring boat Gjöa. The first single-season transit was achieved in 1944, when Sergeant Henry A. Larsen, of the Royal Canadian Mounted Police, made it through in a schooner.