This 1950s movie epic was not a hit, but had a particularly superduper superstar set of headliners, Cary Grant, Frank Sinatra and Sophia Loren. Sinatra was seriously miscast as a firebrand Spaniard fighting valiantly against Napoleon's armies in 1810, and Grant also seems out of place, but otherwise it is still an impressive big-budget production for its day.
For me, Sophia's sexy flamenco dance showcase early in the film easily upstages the huge gun our heroes are dragging along 1,000 kilometers of Spain to do battle at Avila. The movie was obviously the inspiration for the 1966 "Combat!" episode titled "The Gun".
Main problem here is that the screenplay by Edward Anhalt, working with his wife Edna Anhalt, is simply not compelling, especially considering his work on many great movies ranging from "Becket" to "Hour of the Gun".
Producer-director Stanley Kramer has become, in recent decades, demoted to relative obscurity. Currently his major works, movies with serious messages, are of no interest, while his contemporary Kubrick is often considered the greatest of all time, and the work of his current counterpart Ridley Scott is laughably overrated. I chalk it up to the preference by both critics and audiences for style over substance.