Kang was born on 22 December 948 into a prominent aristocratic family in the hyeon of Geumju (now Gwanak District, Seoul).

His father also worked for the King Taejo of Goryeo, and had been awarded for helping establish a new dynasty and unifying the Korean Peninsula.

In 983, he received the top score in the civil service examination, and qualified as a government official at age thirty-six.

Sŏ Hŭi was sent to General Xiao as Korean representative, and the successful truce negotiation led to the withdrawal of Khitan forces and establishment of friendly relationship between Liao and Goryeo.

Also in 1009, General Kang Cho of Goryeo led a coup against the government; he deposed and murdered King Mokjong and began a military rule, and broke the peaceful relationship with the Khitans.

The Khitans saw this as their reason to attack Goryeo, and in 1010, Emperor Shengzong of Liao led a massive invasion with a contingent of 400,000 soldiers, commanding the troops himself.

Suffering heavy casualties in five major engagements, the Khitans finally defeated the Goryeo army and executed their commander General Kang Cho.

The Khitans gained no benefit from the war; rather spending precious resources in vain and reducing the national treasury.

This time, many officials urged the king to commence peace negotiations, since the damage from the Second Goryeo-Khitan War had been so great, leaving Goryeo difficult to recover.

The victories of General Kang thus marked the ending point of the chain of wars between countries and was the beginning of a triangle diplomacy (Goryeo, Liao, Song), setting the scene for the ascendance of the Jurchens.