sentences:  In 1931, the NAPF became the Union of Japanese Proletarian Cultural Organizations (日本プロレタリア文化連盟, Federacio de Proletaj Kultur Organizoj Japanaj, also known as KOPF), incorporating other cultural organizations, such as musicians and filmmakers.KOPF produced various magazines including "Working Woman" (働く婦人)
  
  The Japanese government cracked down harshly on proletarian authors, as the Japanese Communist Party had been outlawed since its founding in 1922.Though not all authors were associated with the party, the KOPF was, leading to mass arrests such as the March 15 incident.