"President Truman won't allow me to spread the war to China?! Damn coward! I'll ask Congress and the US people for that, and to grant me the permission to use nukes, too!" - General Douglas MacArthur
Seriously, what did he expect Truman's response would be?
Going to have to second spreading the War on Terror to Iraq without finishing it up in Afghanistan first.
Another from WW1: Taking a month between the initial naval bombardment of the Dardenelles Strait and making the landings, among other mistakes.
One from the 18th century - Charles XII trying to invade Moscow and bring Peter the Great to submission the way he did Frederick Augustus of Poland and the king of Denmark-Norway. He did so by lying to his officers when they had laid a plan to attack and retake St. Petersburg. Instead of a quick victory, he ended up taking his men through a death march that cost him the best of Sweden's Carolean army.
Yes, the man was known to win extraordinary risks and win big tactical and strategic gambles, but the invasion of Moscow was big even for him.