Youzhou (734) — the same event in Old Book of Tang and Zizhi Tongjian

Old Book of Tang: Zhang Shougui attacked the Khitan, killed their king Qulie and Ketugan in the camp, and set up Li Guojie as king of the Khitan…

What each source says

Old Book of Tang (Jiu Tangshu), Annals · AD 734 · 幽州

Zhang Shougui attacked the Khitan, killed their king Qulie and Ketugan in the camp, and set up Li Guojie as king of the Khitan.

乙巳,幽州長史張守珪發兵討契丹,斬其王屈烈及其大臣可突幹於陣,傳首東都,餘叛奚皆散走山谷。
Location: 舊唐書 卷8 開元22年 8月

Zizhi Tongjian (Comprehensive Mirror) · AD 734

In June 734 (Renchen day), Zhang Shougui, jiedushi of Youzhou, crushes the Khitan and sends a messenger to report the victory.

六月,壬辰,幽州節度使張守珪大破契丹,遣使獻捷。
Location: 권214 734년 항

Place: 幽州

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