The British sent substantial military forces, while the Royal Navy controlled the Atlantic, preventing France from sending much help. In 1758 the British captured Louisbourg, gaining control over the mouth of the St. Lawrence, and also took control of key forts on the frontier in battles at Frontenac and Duquesne. In spite of the spectacular defeat of the supposed main British thrust in the Battle of Carillon (in which a banner was supposedly carried that inspired the modern flag of Quebec), the French military position was poor.