Complex sentence: At the beginning of the USO riot scene, one of the "extras" dressed as sailors, is actor James Caan; the film also featured the acting debut of Mickey Rourke as Private First Class Reese of Sgt. Tree's tank group.
Split into simpler sentences: At the beginning of the USO riot, one of the "extras" dressed as sailors is actor James Caan. Making his first screen appearance is Mickey Rourke as Private First Class Reese of Sgt. Tree's tank group.