Possible Clues:

• Supremo for the Normandy landings?
• Feudal superior arriving in Normandy
• Old rover (anag.)
• Ruler put too much weight on introducing small change
• Excessive cargo with Roger for a superior
• Ruler; D-Day operation
• Operation - - , WW2 D-Day code
• The big boss of D Day
• Operational name for the Anglo-American invasion of Normandy in 1944
• Ruler, D-day Operation