The enriched nuclear fuel could be used to operationalize a nuclear bomb. Iran had a history of using illegal poison gas in the Iraq-Iran War (Both sides used chemical weapons.) Iran had a history of aiding terrorist organizations. And Iran is the only nation belonging to the UN and sighing its charter in modern history that has threatened to destroy another nation via their President whose threats had not been retracted. Iran also is a Shiite Moslem nation and is at odds with the Sunni Moslem countries of the Middle East and if the Iraqis developed a nuclear bomb, there would be a Middle Eastern nuclear arms race. If Iraq would not cease its development program under pressure from other nations, a military attack was the other option. All were indeed ugly.