Stilwell's caustic personality was reflected in his nickname 'Vinegar Joe'. Although distrustful of his allies Stilwell showed himself to be a capable and daring tactician in the field but a lack of resources meant he was continually forced to improvise. He famously differed as to strategy, ground troops versus air power, with his subordinate, Claire Chennault, who had the ear of Generalissimo Chiang Kai-shek. George Marshall acknowledged he had given Stilwell 'one of the most difficult' assignments of any theater commander.