Yakuza in JapaneseThe Yakuza are the largest mafia type organisation in the world and their origins can be traced back to the end of the Shogunate era in 1868 as the 500,000 Samurai were gradually replaced by the Imperial Army of the Meiji government. While many of the Samurai found new roles in the modernisation of Japan, many were disaffected and became masterless ronin. Of those who did not take up a new trade or become merchants, some became protectors of small villages and hamlets while others preyed on the same. Japanese Yakuza 
History and Cultural Development by Christopher Altman provides a neat summary of their beginnings.  

Yamaguchi-gumi crestThe Yakuza were considered to be underdogs and protectors by many in Japanese society so have become more tolerated, until recently, by successive governments. They developed into numerous syndicates (largest being Yamaguchi-gumi) and chapters (Kobe is the stronghold) always attracting outcasts, including many Koreans or Japanese from Korean descent. Wikipedia explains the origins, history, different syndicates, their activities and the impact of the Koreans amongst other bits and pieces.


Yakuza processionAfter WWII their membership and influence grew rapidly as their numbers swelled to 184,000 in 5,200 chapters. While the occupying Americans felt uneasy with their presence, the Yakuza as a nationalistic force were seen as a counter balance to the sympathies for Communism among other disenchanted members of society. As Japan recovered from the war and prospered in the 80s and 90s their membership declined but there are still over 100,00 members in 2,500 chapters. Their activities range from gambling, prostitution, including human trafficking, extortion, white-collar crime to legitimate business and substantial political influence. They discourage theft and many syndicates do not allow drug trafficking. Another good article is by Anthony Bruno.

The Yakuza have international connections, particularly in the United States as well as in Australia.