7 events the sources record for this year, grouped by region.
What happened
China (3)
Crown Prince Li Ying and the princes of E and Guang were reduced to commoners and all were killed. (New Book of Tang (Xin Tangshu), Annals 新唐書 卷005 睿宗·玄宗 開元25年4月)
In 737, Cui Xiyi, compelled, sends troops from Liangzhou and goes south more than 2,000 li into Tubo territory, fights west of Qinghai, routs them and beheads more than 2,000; Qili Xu escapes with only his body. (Zizhi Tongjian (Comprehensive Mirror) 권214 737년 항)
Japan (4)
Mutsu inspector Ōno no Azumahito asks for the punishment of Ōkachi village of the Emishi to open a direct route to Dewa; Fujiwara no Maro is sent as envoy with the sword of authority. (Shoku Nihongi (Continued Chronicles of Japan) 續日本紀 卷第12 「丙申。先是。陸奧按察」)
The envoy to Silla reports that Silla lost courtesy and did not accept the envoy's message; all officials from fifth rank up and sixth rank down are asked to give their opinions. (Shoku Nihongi (Continued Chronicles of Japan) 續日本紀 卷第12 「己未。遣新羅使奏新羅」)
Fujiwara no Maro arrives at the Taga palisade in Mutsu on the nineteenth day of the second month; consulting with Ōno no Azumahito, he gathers 1,000 cavalry from six provinces and opens two routes, mountain and sea, to win over the Emishi. (Shoku Nihongi (Continued Chronicles of Japan) 續日本紀 卷第12 「戊午。遣陸奧持節大使」)
The epidemic of smallpox greatly rises in spring, beginning in Tsukushi; from summer to autumn, people from court nobles downward die in succession. (Shoku Nihongi (Continued Chronicles of Japan) 續日本紀 卷第12 「是年春。疫瘡大發。初」)