 Charles abdicated as emperor in 1556 in favour of his brother Ferdinand; however, due to lengthy debate and bureaucratic procedure, the Imperial Diet did not accept the abdication (and thus make it legally valid) until 24 February 1558.Up to that date, Charles continued to use the title of emperor.Much of Charles's reign was taken up by conflicts with France, which found itself encircled by Charles's empire while it still maintained ambitions in Italy.