“Dear Comrades!” is inspired by a true story: It takes place over a few days in 1962 in the city of Novocherkassk, Russia, where the Khrushchev Kremlin has just announced hikes in food prices at the same time that industrial workers are ordered to increase their production quotas. Employees at a locomotive plant go on strike, resulting in two days of unrest and government crackdown, ultimately ending in a massacre at the hands of the KGB. Kept secret for 30 years, the episode was finally brought to light in the 1990s.
Source: https://www.washingtonpost.com/