Which nation was able to broker an armistice agreement between north and south korea, ending the fighting?

The Armistice Agreement to end the war between the two Korean nations was brokered by India.

Explanation:

The Korean Armistice Agreement was signed on July 27, 1953 by U. S. Army Lieutenant General William Harrison, Jr. representing the United Nations Command, the Chinese people's Volunteer Army (PVA) and North Korean General Nam II representing the Korean People's Army. This agreement brought about the complete cessation of the hostilities of the war.  

India played a mediator in the war, bringing resolutions to ensure peace and ceasefire between the warring nations. The war had never formally ended and this armistice was the truce that will bring the nations into a standstill until further solutions could be found. This armistice suggested the establishing of a Neutral Nations Repatriation Commission (NNRC) chaired by Indian General K. S. Thimayya, which will decide the fate of over 20,000 prisoners of war (POWs) from both sides, among the many issues to be resolved. Though this armistice was not the final solution for the war to stop, it brought a piece of relief for the people and also for the governments until a permanent solution can be found.