Soon after the beginning of the Seven Years' War, through the influence of Madame de Pompadour, he was put in command of a corps of 24,000 men, and in November 1757 he sustained the crushing defeat of Rossbach. Along with the failure to hold Hanover following the Invasion of Hanover (1757) this marked a dramatic turnaround for French fortunes as just months before they had seemed on the brink of victory in Europe.