Peace with the Iroquois began to fall apart in the 1630s and conflicts broke out in June 1641, with hostilities lasting more than a quarter of a century. In August 1642, reinforcements of forty soldiers arrived. Soon after, the Queen of France, interested in the Canadian missions, financed the raising and outfitting of a company of sixty soldiers that landed in Quebec City in June 1644. Twenty-two of these soldiers went "to the Hurons," the mission of Sainte-Marie (near present-day Midland, Ontario) until 1645. This was the first time that a French garrison was sent that far west.

     Since it was costly to employ soldiers, trading companies like the Compagnie des Cent-Associés hired as few as possible. In 1645 there were perhaps sixty soldiers in the colony, even though according to an agreement signed in March that year, at least a hundred were supposed to be maintained. In actual fact, few if any soldiers landed in Quebec City and towards 1652 there were only about 35 professional soldiers left in the colony. Fortunately, the French and the Iroquois made peace in the fall of 1653.

     However, combats resumed in 1658, and the Iroquois had the advantage thanks to their superior numbers and guerilla tactics. Despite appeals from her colony, France sent no reinforcements, and the French had to respond as best they could to the Amerindian raids. This was the setting for the adventures of Adam Dollard des Ormeaux, officer of the Montreal garrison, along with his sixteen companions, several of them soldiers. All were killed fighting the Iroquois in Long-Sault (near present-day Carillon, Québec) in the spring of 1660. In 1661 and 1662, two hundred soldiers arrived in Canada, but the effects of these reinforcements were scarcely felt against the numerous Iroquois.