Cook joined the British merchant navy as a teenager and joined the Royal Navy in 1755. He saw action in the Seven Years' War and subsequently surveyed and mapped much of the entrance to the Saint Lawrence River during the siege of Quebec, which brought him to the attention of the Admiralty and the Royal Society. This acclaim came at a crucial moment in his career and the direction of British overseas exploration, and led to his commission in 1766 as commander of HMS "Endeavour" for the first of three Pacific voyages.