Emperor Taizong of Tang used Yeon Gaesomun's murder of King Yeongnyu of Goguryeo as the pretext for his campaign and started preparations for an invasion force in 644. General Li Shiji commanded an army of 60,000 Tang soldiers and an undisclosed number of tribal forces which gathered at Youzhou. Emperor Taizong commanded an armored cavalry of 10,000 strong.
Emperor Taizong of Tang used Yeon Gaesomun's assassination of King Yeongnyu of Goguryeo as a justification for his military action and initiated preparations in 644. General Li Shiji commanded an army consisting of 60,000 Tang soldiers and tribal forces that assembled at Youzhou. Emperor Taizong led a powerful armored cavalry force.