Sir Henry Clinton's legacy in the eyes of historians has been mixed. He held the command in America for four years, ending in disaster, and as a result, he is widely seen to share in the blame for the defeat. Biographer William Willcox, in his analysis of Clinton's tenure in North America, observes that at times "Sir Henry's ideas were not carried out for reasons that lay to some extent within himself", and that he and Admiral Graves "apparently ignored the danger" of de Grasse in 1781. However, Willcox notes that campaign plans Clinton formulated for 1777, 1779 and 1780 were frustrated by external events he could not control, and Willcox generally blames Cornwallis for the failure of the Carolina campaign. In contrast, Cornwallis' biographers Franklin and Mary Wickwire point out that Cornwallis' failures are at least partially attributable to directives of Clinton that left him with relatively inadequate troop strength and irregular supply lines.