[1][2] Three major proletarian parties emerged during 1926, all closely linked to trade unions active in Japan.
[7][4] The proletarian parties took part in the 1927 prefectural assembly elections, and their participation was closely watched.
Moreover, socialist ideas and movements were treated with a great deal of suspicion by many Japanese voters, limited the appeal of the proletarian parties.
[6] Furthermore, the electoral campaigns of the proletarian parties suffered from direct sabotage by state authorities.
[12][13] In 1929, Labour-Farmer Party leader Oyama Ikuo faced criticism from a former associate, Mizutani Chozaburo, for being too open towards a merger with the centrist sectors of the socialist movement.
Mizutani founded the Labour-Farmer Masses Party in January 1929 and saw its appeal largely confined to Kyoto.
Notably, the main backer of the Social Democratic Party, Sodomei, did not oppose the Incident.