Eisenhower's greatest weapon wasn't a tank or a plane. It was his ability to make difficult men work together.
The Allied Supreme Command (SHAEF) was a diplomatic minefield. Eisenhower had to balance the egos of Montgomery (British), Patton (American), and De Gaulle (French), all while answering to Roosevelt and Churchill.
He operated on a simple, unbreakable principle: Unity of Command. No national interest could supersede the mission objective.
Generals like Montgomery wanted total control of ground forces. Patton wanted to race ahead regardless of supply lines. De Gaulle wanted to liberate Paris immediately for political reasons.
Eisenhower acted as the supreme arbiter. He soothed egos when possible, but fired commanders when they threatened the coalition's unity. He famously said, "I will fight with a broken army, but I will not fight with a broken coalition."