Pictured: Cadets of the Kharkov NKVD Service Dog Training School, 1934.

On December 29, 1921, the Criminal Investigation Department established the Central Kennel for Service and Detective Dogs in Moscow, and in 1923, the NKVD Central Kennel School, which trained Detective Dog handlers, was established. Similar schools began to open in many major cities across the country.
In 1930, the criminal investigation department already had 130 search dog handlers and 221 dogs:
German Shepherds - 180;
Doberman pinschers - 35;
Airedale Terriers - 1;
Belgian Shepherds - 1;
Rottweilers - 1;
Laikas - 3.