Although a competent and capable General, Arnold's career was full of mishaps, problems and passed blame, despite fighting valiantly and vigorously for the cause, even sacrificing his own leg. Towards the end, he felt that his services were being overlooked while others were be given rewards which he believed should be his. This was his motivation for betraying the American forces.
Ironically, although providing him handsomely (though not the amount he was promised, as he had failed to surrender West Point), the British never completely trusted Arnold, fearing he would betray them and return to the Patriots. As such he was provided with no major military tasks for the remainder of the war, and was later given a minor role in England.
Following the war, he lived out the rest of his life in England, save a short period where he lived in Canada. He died mostly unknown, having never really amounted to much. According to legend, his last words were "Let me die in the old uniform in which I fought my battles for freedom, May God forgive me for putting on another."