Siege of Louisbourg ( 1745 ) The Siege of Louisbourg took place in 1745 when a New England colonial force aided by a British fleet captured Louisbourg , the capital of the French province of Île - Royale ( present - day Cape Breton Island ) during the War of the Austrian Succession , known as King George ' s War in the British colonies . Although the Fortress of Louisbourg ' s construction and layout was acknowledged as having superior seaward defences , a series of low rises behind them provided attackers places to erect siege batteries . The fort ' s garrison was poorly paid and supplied , and its inexperienced leaders mistrusted them . The colonial attackers were also lacking in experience , but ultimately succeeded in gaining control of the surrounding defences . The defenders surrendered in the face of an imminent assault . Louisbourg was an important bargaining chip in the peace negotiations to end the war , since it represented a major British success . Factions within the British government were opposed to returning it to the French as part of any peace agreement , but these were eventually overruled , and Louisbourg was returned , over the objections of the victorious colonists , to French control after the 1748 Treaty of Aix - la - Chapelle . Prelude . The mutual declarations of war between France and Britain in 1744 were seen as an opportunity by British colonists in New England who were increasingly wary of the threat Louisbourg posed to their fishing fleets working the Grand Banks of Newfoundland . The wariness bordered on an almost fanatical paranoia or a religious fervour , stirred by false accounts of the size and scale of Louisbourg ' s fortifications and the general anti - French sentiment shared among most British colonists at the time . New Englanders ' paranoia increased after a small French force sailed from Louisbourg in the summer of 1744 to the nearby British fishing port of Canso , attacking a small fort on Grassy Island and burning it to the ground . This port was used by the New England fishing fleet as it was the closest mainland North American British port to the fishing grounds ; however , the Canso Islands ( including Grassy Island ) were contested by both Britain and France . The prisoners taken during the Canso raid were first brought to Louisbourg , where they were given freedom to move around . Some of the military men took careful note of the fortress design , layout and condition , as well as the size and condition of its garrison and armaments . These men were eventually released to Boston , where their intelligence , along with that provided by merchants who did business at Louisbourg , proved useful in planning the attack . The French , military and civilian alike , were not in the best of condition at Louisbourg . Supplies were short in 1744 , and the fishermen were reluctant to sail without adequate provisions . The military rank and file claimed that it was promised a share of the spoils from the Canso raid , which had instead gone to officers , who sold those same provisions and profited in the endeavour . In December 1744 , the troops mutinied over the poor conditions and pay that was months overdue . Even after acting Governor Louis Du Pont Duchambon managed to quiet the discontent by releasing back pay and supplies , the following winter was extremely tense , as the military leadership maintained a tenuous hold on the situation . Duchambon was even reluctant to send for help , fearing the message would be intercepted and spark further unrest . Word of the unrest did , however , make its way to Boston . Battle . In 1745 , the governor of the Province of Massachusetts Bay , William Shirley , secured by a narrow margin the support of the Massachusetts legislature for an attack on the fortress . He and the governor of the Province of New Hampshire , Benning Wentworth , sought the support of other colonies . Connecticut provided 500 troops , New Hampshire 450 , Rhode Island a ship , New York ten cannons , and Pennsylvania and New Jersey funds . The force was under the command of William Pepperrell of Kittery ( in the portion of the Massachusetts colony that is now the state of Maine ) , and a fleet of colonial ships was assembled and placed under the command of Captain Edward Tyng . Governor Shirley sent a request to Commodore Peter Warren , the chief officer of the Royal Navy ' s West Indies station with a request for naval support in the event of an encounter with French warships , which would significantly outclass any of the colonial ships . Warren at first declined this offer , lacking authorization from London to assist . Only a few days later , he receive orders from the Admiralty to proceed to protect the New England fisheries . The expedition set sail from Boston in stages beginning in early March 1745 with 4 , 200 soldiers and sailors aboard a total of 90 ships . The force , beginning to take on the air of a religious crusade , stopped at Canso to reprovision . There they were met by Commodore Warren , enlarging the expedition by 16 ships . In late March , the naval forces began to blockade Louisbourg , however ice fields were being swept from the Gulf of St . Lawrence to the seas off Louisbourg that spring , presenting a considerable hazard to wooden - hulled sailing ships . The poor weather and general state of disorganization of the New England naval forces resulted in numerous delays to the expedition , however , they kept busy harassing French fishing and shipping in the waters surrounding Île - Royale . With the ice fields gone by late April , the siege began in earnest . Pepperell ' s land forces sailed in transports from Canso . On May 2 , he besieged Port Toulouse ( present - day St . Peter ' s , Nova Scotia ) as well as destroying several coastal villages in the area between Canso and Louisbourg . The New England force then landed May 11 southwest of Louisbourg at Gabarus Bay in a flanking manoeuvre and proceeded overland with their cannon on sleds designed by Lieutenant Colonel Nathaniel Meserve of the New Hampshire Militia who was a shipwright by trade , to the series of low hills overlooking the western walls of the fortress . Except for a small party led by Pierre Morpain , the fortress ' naval commander , the landing on May 11 of the New England colonial forces and advance on the fortress went unopposed . The French were not helped by the fact that the government in Paris had advance knowledge of the New Englanders ' intentions to attack , but the decision was made not to augment defences or send reinforcements . The French defenders were seriously outmanned , and Duchambon ' s distrust of his troops and fears that they would desert led him to keep his soldiers within the walls of the fortress rather than confronting the colonial forces at the landing site . The French defenders of the strategically important Island Battery successfully stopped several assaults , inflicting heavy losses on the New England troops . However , the New Englanders eventually established gun batteries at Lighthouse Point that commanded the island , leading to its abandonment by its defenders . On June 15 , French and native reinforcements led by Paul Marin were prevented from reaching Louisbourg in the Naval battle off Tatamagouche . The New Englanders ' landward siege was supported by Commodore Warren ' s fleet and , following 47 days ( 6 weeks and 5 days ) of siege and bombardment , the French capitulated on June 28 , 1745 . News of the victory reached Governor Shirley in Boston on July 3 which , coincidentally , was commencement day at Harvard ( usually a day of celebration in itself ) . All of New England celebrated the taking of France ' s mighty fortress on the Atlantic . Aftermath . Losses to the New England forces in battle had been modest , although the garrison that occupied the fortress during the following winter suffered many deaths from cold and disease . After the fall of Louisbourg , the New Englanders also assumed control of Port - La - Joye on present - day Prince Edward island ( which the French regained in battle the following year ) . Duchambon ' s actions in the mutiny and siege were the subject of inquiries upon his return to France in August 1745 . Duchambon was protected from reprisals by the actions of François Bigot , Louisbourg ' s civilian administrator , who deflected much of the blame onto others . Duchambon retired from the service with a pension in March 1746 . William Pepperrell and Peter Warren were both richly rewarded for their efforts . Warren , in addition to profiting from prize money , was promoted to rear admiral . Pepperrell was made a baronet by King George II and given a commission as colonel of a new regiment , numbered 66th at the time ( but not to be confused with the later 66th Regiment of Foot ) . Governor Shirley was also given a colonel ' s commission to raise his own regiment . Both France and Britain planned expeditions to North America in the wake of the capture . The great Duc d ' Anville Expedition led by Admiral Jean - Batiste , De Roye de la Rochefoucauld , Duc d ' Anville was dispatched from France to retake Louisbourg and recover Acadia in 1746 . However it was destroyed by storms , disease and British naval attacks and never reached the fortress . The British government made plans , based on suggestions by Shirley and Warren , for a follow - up expedition to seize Quebec . For a variety of reasons , including a late start and contrary winds , the 1746 expedition did not leave European waters , and was instead diverted to raid the French port of Lorient . Although the idea was also considered for the 1747 campaign season , it again failed to bear fruit . When the war ended with the signing of the Treaty of Aix - la - Chapelle in 1748 , Louisbourg was returned to France in exchange for the return of Madras to Britain , and the withdrawal of French troops from the Low Countries . The decision to withdraw from Louisbourg came under fierce attacks in London from opponents of the Pelham Ministry , but it went ahead nonetheless . In 1758 the fortress was captured again by the British during the Seven Years ' War , this time permanently , as Île - Royale and much of New France was ceded to Britain under the terms of the 1763 Treaty of Paris .