Chicago Reader review:
Made in 1940, when a sense of humor about the Nazis was still possible. Charles Chaplin plays two roles, Adenoid Hynkel, the dictator of Tomania, and a poor Jewish barber who's mistaken for Hynkel and sent to deliver a speech in his place. The final address, in which Chaplin pleads with the audience for sanity and world peace, has often been criticized for its length and sententiousness, but it is a remarkable piece of acting and verbal rhetoric (all the more so as this was the first time Chaplin had spoken in a film). Chaplin is at his most profound in suggesting that there is much of the Tramp in the Dictator, and much of the Dictator in the Tramp.
Here (and above) is the trailer.