After the death of Colonel George Monro, the former Assassin Shay Cormac was formally inducted into the Colonial Rite of the Templar Order by its Grand Master, Haytham Kenway. After a few days, Cormac and Kenway met in New York, and after a brief discussion about Isu temples, Haytham informed Shay about Assassin activity near the Fort of Louisbourg.
Shay was also informed about the Royal Navy officer and explorer, James Cook, and his usefulness to the Templars, despite the lack of knowledge of the Order's existence on the captain's part. Shay and his quartermaster, Christopher Gist, met with James Cook and Haytham aboard the former's Man O' War, HMS Pembroke. Cook informed the Templars that a Royal Navy fleet had already set sail for Louisbourg, but the he was worried about the French defenses. Grand Master Kenway insisted on attacking the fort, and eventually convinced Cook to participate. Cook in turn offered command of his ship to Shay, for the duration of the battle.
On the day of battle, HMS Pembroke was approaching Louisbourg, escorted by two frigates. As the ships neared the fort, mortars fired by the French Men O' War destroyed one of the escort ships. In retaliation, Shay used the Pembroke's firepower to destroy a considerable portion of the French Navy.
After a successful counter-attack, the ship of Assassin Adéwalé, the Experto Crede, led several fireships into the fray, destroying the last escort. Under the advice of Gist, Shay did not attack the Assassin's brig, focusing on the fireships instead. After destroying about ten of those ships, another wave of French ships arrived along with four more fireships. Cook, thinking the situation was hopeless, advised Shay that they should fall back, but Shay continued to press the attack instead. Eventually, the fireships were joined by French reinforcements, but they were immediately assaulted by the arrival of British reinforcements. This allowed the rest of the Royal Navy, which later arrived with an astonishing forty Men O' War, to launch an offensive on the fort itself, and capture Louisbourg.
The Siege of Louisbourg proved to be the turning point of the Seven Years' War, weakening the French that eventually led to the capture of Montreal and Quebec by Amherst and Wolfe respectively. Adéwalé's interference made him a target for the Templars, which was capitalized on by Shay and Haytham, who tracked down and eliminated him at Vieille Carrière.