11 events the sources record for this year, grouped by region.
What happened
China (3)
Ma Ju attacked Pang Xun at Huanhe; Pang Xun drowned, and the Xuzhou rebellion was suppressed. (Old Book of Tang (Jiu Tangshu), Annals 舊唐書 卷19上 咸通10年 9月)
On the first day of the second month, the emperor, sitting in audience (rinken), makes Prince Sadaaki (later Emperor Yōzei) crown prince and reads the investiture document. (Nihon Sandai Jitsuroku 卷第十六 貞觀11年2月 (원문 16.26))
On the thirteenth day of the fourth month, the compilation of the Jōgan-kaku (Jōgan regulations) is complete, and Great Counselor Fujiwara no Ujimune and others present it at court. (Nihon Sandai Jitsuroku 卷第十六 貞觀11年4月十三日 (원문 16.82))
On the twenty-sixth day of the fifth month, a great earthquake strikes Mutsu province: the sky shines like daytime, castle walls, storehouses and gates collapse, the sea roars and a tsunami surges up to the foot of Taga castle; more than a thousand people drown (the Jōgan earthquake and tsunami). (Nihon Sandai Jitsuroku 卷第十六 貞觀11年5月廿六日 (원문 16.86))
On the fifteenth day of the sixth month, Dazaifu reports that on the night of the twenty-second of last month, Silla pirates came to Hakata port in two ships, plundered the tribute silk and floss of Buzen province and fled. Troops were sent in pursuit but failed to capture them. (Nihon Sandai Jitsuroku 卷第十六 貞觀11年6月十五日 (원문 16.90))
On the fourteenth day of the seventh month, in Higo province a heavy storm and tidal wave flood six districts; people and livestock are crushed, and more than half of the official goods are lost. (Nihon Sandai Jitsuroku 卷第十六 貞觀11年7月十四日 (원문 16.112))
On the seventeenth day of the twelfth month, after last summer's plunder of tribute by Silla pirates, a strange event occurs: a large bird gathers at the Dazaifu office and the armory. The Jingikan and the Onyōryō divine that a neighboring country's war may come, so offerings are made in the provinces of the Five Capitals and Seven Circuits. (Nihon Sandai Jitsuroku 卷第十六 貞觀11年12月十七日 (원문 16.220))
On the twenty-eighth day of the twelfth month, Right Guard Lieutenant Sakanoue no Takimori is sent to Dazaifu to handle prayers and vigilance. He proposes that, since Hakata is the port where neighboring ships gather, near the Kōrokan there be one commander (tōryō), forty ship soldiers (senshi) and forty suits of armor. (Nihon Sandai Jitsuroku 卷第十六 貞觀11年12月廿八日 (원문 16.232))
Western Europe (1)
The army returned to York and stayed there a year. (Anglo-Saxon Chronicle Giles/Ingram 1847 A.D. 869 항 (pg657.txt 줄 2747))