The Polish Operation of the NKVD (Soviet security service) in 1937–1938 was an anti-Polish mass-ethnic cleansing operation of the NKVD carried out in the Soviet Union against Poles (labeled by the Soviets as "agents") during the period of the Great Purge. It was ordered by the Politburo of the Communist Party against so-called "Polish spies" and customarily interpreted by NKVD officials as relating to 'absolutely all Poles'. It resulted in the sentencing of 139,835 people, and summary executions of 111,091 Poles living in or near the Soviet Union. The operation was implemented according to NKVD Order No. 00485 signed by Nikolai Yezhov. The majority of the shooting victims were ethnically Polish, but not all, with some belonging to various minority groups from the Kresy macro-region, for instance, Ruthenians; these groups in the Soviet worldview had some element of Polish culture or heritage, and were therefore also "Polish". The remainder were 'suspected' of being Polish, without further inquiry, or classified as possibly having pro-Polish sympathies. The NKVD agents looked through local phone books to expedite the procedure and detained people with names that sounded Polish. The Polish Operation was the largest ethnic shooting and deportation action during the Great Purge campaign of political murders in the Soviet Union. NKVD Order № 00485 The top secret NKVD Order No. 00485, titled "On the liquidation of the Polish diversionist and espionage groups and POW units," was approved on August 9, 1937 by the Party's Central Committee Politburo, and was signed by Nikolai Yezhov on August 11, 1937. It was distributed to the local subdivisions of the NKVD simultaneously with Yezhov's thirty-page "secret letter," explaining what the "Polish operation" was all about. The letter from Yezhov was titled, "On fascist-resurrectionist, spying, diversional, defeationist, and terrorist activity of Polish intelligence in the USSR". Joseph Stalin was approving of the operation saying "‘Very good! Dig up and purge this Polish espionage mud in the future as well. Destroy it in the interest of the USSR.." The "Order" adopted the simplified so-called "album procedure" (as it was called in NKVD circles). The long lists of Poles condemned by a lower NKVD organ (so-called dvoika, a two-man team) during early meetings, were then collected into "albums" and sent to the midrange NKVD offices for a stamp of approval by a troika (a three-man team; a communist official, NKVD leader, and party procurator). Poles were the first ever major