The British commander that was sent to conquer the French in the Ohio River Valley was John Forbes. He captured the French outpost of Port Duquesne. The campaign is known as the Forbes Expedition. The objective of the expedition was to displace the French from the area in preparation for a later invasion to Canada.
It was primarily the "Reconstruction Act" that forced states to accept the Fourteenth Amendment in order to join the Union, since this led to a military oversight of the Southern states immediately after the Civil War.