It's the mostly liked by the several generations of the Russian people comedy of Leonid Gaidai together with 'Operatsiya Y' and 'Kavkazskaya plennitsa', full of light irony and brilliant folksy humor of the late soviet time. The performance of the main actors (Andrei Mironov, Yuri Nikulin and Anatoli Papanov) is absolutely superb. Perhaps though it's not much appreciated amongst some high-minded intellectuals, which have their own cinema.
Review of The Diamond Arm
