The timing of the release, coming months after the Nazi conquest of France, ensured it had massive publicity, but it had interest from movie-watchers even before then. On Feb. 7, 1939, the Chicago Tribune's Hollywood columnist opined that "the Charles Chaplin production of a film to be called 'The Dictator' should answer the question whether the comic genius of the silent films has weathered or withered since talking pictures extinguished his own medium."

Production began about the same time that Germany invaded Poland. By summer 1940, with France invaded, columnist Ed Sullivan concluded, "It is one thing to construct a satirical comedy about dictators, but when one of them seizes half of Europe, the subject no longer may be considered comical." A few weeks later, Sullivan talked to Chaplin and said he was told that Chaplin "is sorry he couldn't have put it out six months ago."

The film went over schedule and over budget, with Chaplin obsessively controlling each element of production. Advance publicity was positive, with The New York Times reporting two months before the premiere that "the rumors add, incidentally, that it is a masterpiece." The movie premiered Oct. 15, 1940 in New York City and was met with generally positive reviews. Bosley Crowther, reviewer for the Times, called it "a superlative accomplishment by a great and true artist," but noted that the film wasn't without its flaws, including its length. As the Times wrote in regard to attendance, "the initial public reaction to Charlie Chaplin's 'The Great Dictator' was very favorable, according to both attendance yesterday and advance ticket sales, the managements of the Astor and Capitol theatres reported."

Others who reviewed the film found its negatives outweighed the positives. One writer in the Times asked, "Every critic, perhaps every member of the audiences, has felt an uneasiness behind the laughter in this film. The pretensions of dictators could be a joke as late as two years ago. Are they now? Is Nazi-occupied France funny? Is martyred London funny? Can the man or men who caused these horrors be considered comic?"

Still others called Chaplin's work "a piece of propaganda" and damned his final speech for being overdone and too heavy-handed. Chaplin himself responded to those remarks, saying in part, "As to Hitler being funny, I can only say that if we can't sometimes laugh at Hitler then we are further gone than we think. There is a healthy thing in laughter, laughter at the grimmest things in life, laughter at death even."

The National Board of Review rated it the second-best movie of the year, behind Grapes of Wrath. The New York Times named it one of the 10 best films of the year. It was nominated for five Academy Awards but didn't win any. Chaplin won the New York Film Critics award in 1940 for "The Dictator," but he famously blew it off and said the award was "meaningless."

By January 1941, it was so well-known that the Mutual Broadcasting System hired Chaplin to deliver the closing speech from the film in a concert celebrating the inauguration of President Roosevelt's third term. The film was distributed in Europe as Allied armies advanced. Eisenhower famously ordered a French translation played in France after the invasion at Normandy. There's even a famous story (allegedly told by a former Ministry of Propaganda employee) that Hitler himself obtained a print of the film and saw it twice. I don't have any reliable source on that, unfortunately.

After the war, Chaplin unfortunately became entangled in the Red Scare. "The Great Dictator" became labeled as communist-leaning, and Chaplin himself was forbidden from returning to the United States. Though that decision was later revoked, didn't return to the United States for 20 years, only coming back to accept a lifetime achievement Academy Award in 1972 as his health declined.