月氏 / Yuezhi
月氏 / Yuezhi enters the wiki through Hanji 175 as the western neighbor used in 头曼单于’s attempted removal of 冒顿单于. Touman sends Modu there as hostage and then attacks Yuezhi, which gives Yuezhi reason to kill the hostage before Modu escapes.
The episode later returns to Yuezhi after Modu takes power. Once 东胡 is destroyed, Modu attacks Yuezhi; the source says some Yuezhi move west toward the Amu Darya region as Da Yuezhi while remaining groups are called Xiao Yuezhi. The page keeps that migration note source-scoped because this ingest is about Modu’s rise and early Han frontier pressure rather than a full Yuezhi history.