Editing Balhae (section)

===Relations with Japan===
Japanese records indicate that Balhae and Japan enjoyed very amicable relations. When King Mu sent Balhae's first envoy delegation to Japan in 727, the mission was made up of 24 men, which included high-ranking generals such as 
Ko Inŭi and Ko Chedŏk. King Mu had 300 sable furs sent by the Balhae delegation to Japan as both a show of goodwill and a desire to foster friendly relations with Japan.<ref>{{cite book |last1=Kim |first1=Eun Gug |chapter=An Enduring Window between North and South: Parhae and Silla |title=A New History of Parhae |date=2012 |publisher=Brill |page=78}}</ref>

Muye's son and successor, [[Dae Heummu]] (Da Qinmao, r. 737–793), continued the course of reconciliation with the Tang. At the same time, trouble with the [[Tibetan Empire]] to the west forced the Tang to withdraw all military forces from [[Korea]] and adopt a defensive stance. Heummu cemented the geopolitical balance by sending an envoy to the Japanese court, which his father had done as well in 728 to threaten Silla with an ally from the southeast. Balhae kept diplomatic and commercial contacts with Japan until the end of the kingdom. Balhae dispatched envoys to Japan 34 times, while Japan sent envoys to Balhae 13 times.<ref>[http://english.historyfoundation.or.kr/his/acij.asp?pgcode=040201 9 Balhae and Japan] {{webarchive|url=https://web.archive.org/web/20150626104047/http://english.historyfoundation.or.kr/his/acij.asp?pgcode=040201 |date=26 June 2015 }} Northeast Asian History Foundation</ref>

Balhae planned a joint attack on Silla with Japan. [[Gyeongdeok of Silla]] offended Japan twice. In 753  he treated Japanese ambassadors with arrogance and in 758 he refused to meet them. After 758, Japan asked Balhae to attack Silla with them. Balhae and Japan exchanged ambassadors several times in the 750s and 760s to plan for the attack. Silla likely knew of these plans and prepared by building six castles along the border with Balhae in 762. The border region changed hands many times but the losses are not described in Silla's official history, only the dates when an army was sent north. Japan prepared a fleet to invade southern Silla; however the plan never came to fruition.{{sfn|Kim|2011a|p=352}}

In 755, the [[An Lushan Rebellion]] broke out, causing the Tang to lose control of the northeast, and even after the rebellion's end in 763, warlords known as [[jiedushi]] controlled the former northeastern part of the Tang empire. In 762, [[Emperor Daizong of Tang]] formally recognized Balhae as a state and Heummu as its king.{{sfn|Wang|2013|p=93}} Although China recognized him as a king, Balhae itself referred to him as the son of heaven (emperor) and a king. The consort of the ruler was also called empress.{{sfn|Sloane|2014a|p=15}}<ref>{{cite web|author=ŔĚżĎąŮ |url=http://www.seelotus.com/gojeon/gojeon/hanmun/ya-cheong-do.htm |script-title=ko:야청도의성(夜聽擣衣聲) |publisher=Seelotus.com |access-date=12 September 2012|language=ko}}</ref> A record in 834 says that Balhae had both kings and great kings. The epitath of Princess Jeonghyo (Zhenxiao), daughter of Heummu, states that his father was a "great king."<ref name = "Kim2014"/>