《魏书·帝纪·卷一》
拓跋郁律向西兼并了乌孙国故地，向东吞并了勿吉族以西的地区，拥有骑士近百万之众。
西兼乌孙故地，东吞勿吉以西，控弦上马将有百万。
Tuoba Yulü annexed the former Wusun Kingdom to the west, annexed the area west of the Wujie tribe to the east, and possessed nearly a million cavalrymen.
<s>[INST] Kindly elucidate the central themes in this passage in English: 西兼乌孙故地，东吞勿吉以西，控弦上马将有百万。 [/INST] Tuoba Yulü annexed the former Wusun Kingdom to the west, annexed the area west of the Wujie tribe to the east, and possessed nearly a million cavalrymen.</s>
Kindly elucidate the central themes in this passage in English: 西兼乌孙故地，东吞勿吉以西，控弦上马将有百万。
user
Tuoba Yulü annexed the former Wusun Kingdom to the west, annexed the area west of the Wujie tribe to the east, and possessed nearly a million cavalrymen.
assistant