Complex sentence: American General Douglas MacArthur, the Supreme Commander of Allied Powers, served as Japan's "de facto" leader and played a central role in implementing reforms, many inspired by the American New Deal.
Split into simpler sentences: American General Douglas MacArthur, the Supreme Commander of Allied Powers, served as Japan's "de facto" leader. Macarthur played a central role in implementing the occupations reforms, many of which were inspired by America's New Deal.