Shamo (軍鶏) is an overall designation for gamefowl in Japan. It generally describes a breed of chicken of Japan which originated in Thailand. The name "Shamo" was a corruption of "Siam" during the early Edo period, but has been selectively bred for several hundred years and is very different from the original stock. In reality, the Shamo is a strain of the Asil (Kaura), taken to Siam (Thailand) and Taiwan and from there to Japan. Its real place of origin is Sindh, Pakistan, secondary place of origin present day India (Hyderabad Dakkan and Rampure). The breed is used as fighting cocks for naked heeled cockfighting in Japan cockfights, where it is still legal. It is also bred all over the world for its show quality and unique upright posture. O-Shamo and Chu-Shamo are designations for different weight categories of large fowl, whereas the Nankin-Shamo is a bantam chicken. The Ko Shamo (シャモ), unlike O-Shamo and Chu-Shamo, is merely an ornamental breed not used for cockfighting, although it is bred to be temperamental and show the spirit of a fighter. While it is not related to the other breeds, it is often assumed to be because of the similarity of their names.
O-Shamo (Large Shamo, 大軍鶏), generally well over 9 lbs