The Siege of Louisbourg occurred from 8 June to 26 July 1758 when the British Army and Royal Navy captured the French fortress of Louisbourg on Ile-Royale amid the French and Indian War.
Louisbourg controlled the approaches to the St. Lawrence River, thus preventing British ships from sailing up the river to attack Quebec. After the failure of John Campbell, 4th Earl of Loudoun's 1757 expedition against Louisbourg, Prime Minister William Pitt the Elder resolved to try again with new commanders. Jeffery Amherst was to lead the capture of the fortress, aided by Admiral Edward Boscawen. The French planned to build up their naval strength around the fortress, but the British blockaded the French fleet sailing from Toulon and defeated a French relief force at the Battle of Cartagena. The French were thus unable to reinforce Louisbourg from the Mediterranean, leaving only 11 ships to defend the city. Five ships were sunk to block the entrance to the harbor, while another was captured on 9 July; only five half-empty ships were left to defend the harbor. Meanwhile, British forces assembled and trained at Halifax before embarking on their ships and departing for Louisbourg on 29 May.
40 men-of-war and 150 transport ships carrying 14,000 soldiers (mostly British Army regulars, plus four companies of American rangers) anchored at Gabarus Bay on 2 June; they were to face 3,500 French regulars and 3,500 marines and sailors. The British attack was delayed by poor weather conditions, but Amherst launched his assault on 8 June. James Wolfe's force suffered heavy losses before William Howe's light infantry secured a beachhead, enabling the rest of Wolfe's division to land. The French retreated back to their fortress, and Wolfe and 1,220 picked men seized Lighthouse Point at the entrance to the harbor. From there, the British shelled and sunk the French ship of the line Le Celebre, and the French ships L'Entreprenant and Le Capricieux also caught fire. On 23 July, a British "hot shot" set the fortress headquarters on fire, reducing French morale. On 25 July, Admiral Boscawen used the thick fog to his advantage and launched a surprise attack that destroyed the last two French ships in the harbor. On 26 July, the French surrendered, and they were ordered to surrender all of their arms, equipment, and flags, being denied the honors of war due to the atrocities committed by their native allies at Fort William Henry. The fall of the fortress led to the loss of French territory across Atlantic Canada, and the British began the second wave of the Acadian expulsion as they took over the rest of the region. In 1759, Louisbourg would serve as a staging area for Wolfe's assault on Quebec City.