During the 1930s mass repression began in the country, and a transit camp for political prisoners sent from western Russia to Kolyma was opened in Vladivostok. The prisoners arrived by train and left on prison ships in terrible conditions. Soviets at first, after 1939 the prisoners came from Eastern Europe and were Japanese POWs after World War II. Factories, ports and cities in the Far East were built by prison labor during the 1930s. After American pilots bombed Tokyo on April 18, 1942, one of the sixteen B-25 bombers landed in Vladivostok when it ran out of fuel; the bomber was confiscated and its crew interned. Although Captain Edward York and his crewmates were well-treated, diplomatic efforts to return them to the United States failed. They were eventually moved to Ashgabat ( from the Iranian border); York bribed a smuggler to help them cross the border and reach a nearby British consulate on 11 May 1943. According to declassified Soviet archives, the smuggling was staged by the NKVD because the Soviet government felt it could not repatriate them legally due to its neutrality pact with Japan.