The reason Wolf came in the back door!
In 1759 Battle of the Plains of Abraham, British troops commanded by General James Wolfe successfully resisted the column advance of French troops and Canadien militia under General Louis-Joseph, Marquis de Montcalm, employing new tactics that proved extremely effective against standard military formations used in most large European conflicts. Both generals were mortally wounded during the battle; Wolfe received three gunshot wounds that ended his life within minutes of the beginning of the engagement and Montcalm died the next morning after receiving a musket ball wound just below his ribs. In the wake of the battle, the French evacuated the city; their remaining military force in Canada and the rest of North America came under increasing pressure from British forces.
France ceded most of its possessions in eastern North America to Great Britain in the Treaty of Paris.