"Sanboku-Isso" was the name given to the four meritorious retainers who received the Emperor Godaigo's favor under the Kemmu Restoration. Their names were Masashige KUSUNOKI, Chikamitsu YUKI, Nagatoshi NAWA and Tadaaki CHIKUSA, and the title of Sanboku-Isso came from all of their names collectively.
The characters used for Masashige's family name were"楠木"(camphor tree) which are read as "kusuno-ki." The characters for Chikamitsu's family name were"結城" and are read as "yu-ki." Nagatoshi was nicknamed "ho-ki" being that he was from Hoki Province. Characters for Tadaaki's family name were "千種" and are read as "chi-gusa" ("gusa" having the same pronunciation as "kusa" which means "grass" in Japanese); their title "Sanboku-Isso" was coined after their names as the character "木" (boku) is also read as "ki" which means "tree," leading to "Sanboku-Isso" which literally means "three trees and one grass."
All four rose to high ranks by winning the "Emperor's favor."
Their periods of prosperity were extremely short. (All four lost their lives during the Kenmu Era in the battle with Ashikaga clan in 1336).
Losing the lives of the four Sanboku-Isso military commanders at an early stage in the battle between the Southern and Northern Dynasties led to an extreme military disadvantage for the Southern Dynasty.