The assassin recounted that OSS Chief William Donovan had ordered the killing on the grounds that Patton had "gone crazy," becoming a major threat to American national interests. Around this same time, a military counter-intelligence field agent began encountering credible reports of a planned assassination plot against Patton and attempted to warn his superiors, including Donovan; not only were his warnings disregarded, but he was repeatedly threatened, and at one point, even placed under arrest. It seems clear that Donovan's orders came from his superiors, either in the White House or elsewhere.
The motivation may or may not have ultimately had a foreign origin. Over the last twenty years, scholars such as John Earl Haynes and Harvey Klehr have exhaustively demonstrated that during the 1930s and 1940s a large network of Communist spies had gained enormous influence in the uppermost reaches of the American government. Indeed, Wilcox carefully documents how the OSS itself had been heavily infiltrated at the highest levels by elements of the Soviet NKVD, and that during this particular period, the two intelligence organizations were in an ambiguous quasi-partnership, with Donovan being especially eager to curry political favor with the pro-Soviet elements near the top of the U.S. government.