In 1689, France and England declared war against each other. By that time, France controlled all of Acadia, most of Quebec, Ontario, the Great Lakes, and the entire Mississippi watershed all the way to the Gulf of Mexico. Britain had been content with the Atlantic coast and with Rupert's Land which encompassed all of Hudson Bay and the Hudson Bay watershed - effectively, all of northern Canada to the Rocky Mountains.
Now, England felt it was time to reclaim Acadia and New France based on John Cabot's original claim of the land back in 1497. Additionally, the Iroquois had increased their hostilities in New France, probably encouraged by their allies, the British. However, when Frontenac's successors, Joseph de la Barre and the Marquis de Denonville, were unable to remedy the hostilities, King Louis XIV felt that only Frontenac's military expertise could end the war quickly and reinstated him as Governor General of New France in October of 1689.
Before his death in 1698, Frontenac succeeded in quelling the Iroquois uprising and successfully defended Quebec from British invasion in King William's War, the first of the French and Indian Wars. Through Frontenac's leadership, France ejected the British from Hudson Bay and captured St. John's in Newfoundland.
Frontenac had entered New France in the midst of a war. He left it in peace.