Louis Joseph was the son of Louis-Daniel de Montcalm and Marie-Thérèse de Lauris and was born at their Chateau d'Candiac in southern France. He became an ensign in the French army at the age of 15. On the death of his father in 1735, he became the Marquis de Montcalm, inheriting the honors, rights, and debts of that position. But his finances were improved soon after by his marriage to Angelique Louise Talon du Boulay. Despite a marriage arranged for money and influence, they were a devoted couple. They made their home at Candiac and had 10 children over the years.
His father puchased a captaincy for him in 1729 and he served in the War of Polish Succession and the War of Austrian Succession, reaching the rank of Colonel of the Auxerrois Regiment in 1743. He was wounded and captured during an Italian campaign of 1745. He was released on parole after several months imprisonment, and promoted to Brigadier for his actions during the campaign.
Montcalm was sent to Quebec in 1756 as the commander of French troops in North America during the French and Indian War. His early campaigns against the British were major succsses. He expanded the defenses at Fort Ticonderoga on Lake Champlain. He captured and destroyed Fort Oswego on Lake Ontario in 1756. His victory at Fort William Henry in 1757 was a military and personal victory, but the conduct of his Indian allies made this a political loss. Later actions at Quebec were less successful and his army was defeated on the Plains of Abraham (near Quebec City) by the British under James Wolfe, and Montcalm died the day after the battle.