Operation Torch Anglo-American invasion of north-western Africa
President Franklin D. Roosevelt gave a direct order that Torch was to have precedence over other operations and was to take place at the earliest possible date, one of only two direct orders he gave to military commanders during the war.
What was the other direct order FDR issued during WWII?
The other direct order they refer to seems to have been in regard to the Battle of the Atlantic and the threat of U-Boats. As the Wikipedia article on the Battle of the Atlantic notes:
Roosevelt ordered King to transfer 60 Liberators from the Pacific theatre to the Atlantic to combat German U-Boats; one of only two direct orders he gave to his military commanders in WWII (the other was regarding Operation Torch).
The long-range B24 Liberators, in combination with technological developments like surface detection radar, helped close the mid-Atlantic gap greatly improving the safety of transatlantic convoys.
It should be noted, however, that President Roosevelt did issue other direct orders to his military commanders during the war. One relatively famous instance was when he ordered General Douglas MacArthur to leave the Philippines in February 1942 (that order was transmitted to MacArthur via General George Marshall). In the event, MacArthur didn't actually leave until March 10.