From the Font of All Wisdom and Knowledge:
In November 1943, Iowa carried President Roosevelt, Secretary of State Cordell Hull, Roosevelt's Chief of Staff Admiral William D. Leahy, Chief of Staff of the Army General George C. Marshall, Chief of Naval Operations Ernest King, Commanding General of the US Army Air Forces Henry "Hap" Arnold, Harry Hopkins, and other military leaders to Mers El Kébir, Algeria, on the first leg of the journey to the Cairo and Tehran conferences. On 14 November, in waters east of Bermuda, USS William D. Porter (DD-579), a destroyer that was part of Iowa's anti-submarine screen, accidentally discharged a torpedo toward Iowa during a drill. Following warnings from the destroyer and her own lookouts, Iowa turned hard to avoid the torpedo, which detonated approximately 1200 yards astern in the ship's wake. Iowa trained her guns on William D. Porter, concerned that the smaller ship might have been involved in an assassination plot.
Iowa completed her presidential escort mission on 16 December by returning the President to the United States. Roosevelt addressed the crew of Iowa prior to leaving by stating, "... from all I have seen and all I have heard, the Iowa is a 'happy ship,' and having served with the Navy for many years, I know—and you know—what that means." He also touched on the progress made at the conference before concluding his address with "... good luck, and remember that I am with you in spirit, each and every one of you."