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.

The northern British colonies regarded Louisbourg as a menace, calling it the "American Dunkirk" due to its use as a base for privateers.

There was regular, intermittent warfare between the French and the Wabanaki Confederacy on one side and the northern New England colonies on the other (See the Northeast Coast Campaigns of 1688, 1703, 1723, 1724).

[3] Although the fortress's construction and layout was acknowledged as having superior seaward defences, a series of low rises behind them made it vulnerable to a land attack.

Louisbourg was an important bargaining chip in the peace negotiations to end the war, since it represented a major British success.

Under the Treaty of Utrecht, which ended the War of the Spanish Succession, the French colony of Acadia had been ceded to Great Britain.

The tribes of Wabanaki Confederacy had a long history of raiding British settlements along Northern New England in present-day Maine.

[4][a] Many of the British military leaders of the siege of Louisbourg came from Northern New England, whose family members were killed in the raids.

In the summer of 1744, New Englanders' concerns of further attacks on the Northern New England increased after a French and Wabanaki force sailed from Louisbourg to the nearby British fishing port of Canso, attacking a small fort on Grassy Island and burned it to the ground, taking prisoner 50 British families.

[5] 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 military rank and file claimed that they were 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.

Connecticut provided 500 troops, New Hampshire 450, Rhode Island a ship, New York ten cannons, and Pennsylvania and New Jersey funds.

Governor Shirley sent to Commodore Peter Warren, the chief officer of the Royal Navy's West Indies station, a request for naval support in the event of an encounter with French warships, which would significantly outclass any of the colonial ships.

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 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.

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.

[14] On May 30, the Mi'kmaq at Chapeau Rouge (L'Ardoise) attacked thirteen English soldiers from Captain Fletcher's crew on the Boston Packet, who were seeking wood and water.

[17] Upon landing, the British forces immediately launched an attack on the North East Harbour (present-day Louisbourg, Nova Scotia).

On June 27, French and native reinforcements led by Paul Marin were prevented from reaching Louisbourg in the Naval battle off Tatamagouche.

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).

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.

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.