Complex sentence: The majority of the German tank forces in Normandy--six and a half divisions--were drawn into the fighting around the town of Caen, where they checked the Anglo-Canadian forces of the 21st Army Group.
Split into simpler sentences: The majority of the German tank forces in Normandy--six and a half divisions, were drawn into the fighting around the town of Caen. Here, they checked the Anglo-Canadian forces of the 21st Army Group.