WATCH: "The eyes of the world are upon you," Gen. Dwight D. Eisenhower told American-led allied troops 75 years ago today. | PBS NewsHour

As Supreme Allied Commander, Eisenhower's greatest challenge wasn't just defeating the enemy, but managing the alliance itself. He welded together the often-conflicting strategies and national pride of British, American, Canadian, and other forces into one effective command. This diplomatic skill was as vital as his military planning. His famous 'D-Day order' invoked a 'Great Crusade' and divine blessing, framing the invasion in moral terms for the troops. After the war, his leadership was deeme