Question: Which two forces have come to the aid of South Korea during The Korean War and, especially, The Battle of Pyongyang?

Context paragraphs:
Battle for Outpost Vegas: The Battle for Outpost Vegas was a battle during the Korean War between the armed forces of the United States and China from March 26–28, 1953, four months before the end of the Korean War.  Vegas was one of three outposts called the Nevada Cities north of the Main Line of Resistance (MLR), the United Nations defensive line which stretched roughly around the latitude 38th Parallel.  Vegas, and the outposts it supported, Reno and Carson, were manned by elements of the 1st Marine Division.  On March 26, 1953 the Chinese army launched an attack on the Nevada Cities, including Vegas, in an attempt to better the position of China and North Korea in the Panmunjon peace talks which were occurring at the time, and to gain more territory for North Korea when its borders would be solidified.  The battle raged for five days until Chinese forces halted their advance after partially obtaining their objective through capturing one outpost north of the MLR on March 28.  The battle for outpost Vegas and the surrounding outposts are considered the bloodiest fighting to date in western Korea during the Korean War.  It is estimated that there were over 1,000 American casualties and twice that number of Chinese during the Battle for Outpost Vegas.  The battle is also known for the involvement of Sergeant Reckless, a horse in a USMC recoilless rifle platoon who transported ammunition and the wounded during the U.S. defense of outpost Vegas.

South Korea–United States relations: Republic of Korea–United States relations (Hangul: 한미 관계 ; Hanja: 韓美 關係 ; RR: "Hanmi gwangye "; MR: "Hanmi kwan'gye " ) have been extensive since 1950, when the United States helped establish the modern state of South Korea, also known as the Republic of Korea, and fought on its UN-sponsored side in the Korean War (1950–1953).  During the subsequent four decades, South Korea experienced tremendous economic, political and military growth, and significantly reduced U.S. dependency.  From Roh Tae-woo's administration to Roh Moo-hyun's administration, South Korea sought to establish an American partnership, which has made the Seoul–Washington relationship subject to some strains, especially with the Anti-US/Korean sentiments.  However, relations between the United States and South Korea have greatly strengthened under the conservative, pro-U.S. Lee Myung-bak administration.  At the 2009 G-20 London Summit, U.S. President Barack Obama called South Korea "one of America's closest allies and greatest friends."  In addition, South Korea has been designated as a Major non-NATO ally.

New Zealand–North Korea relations: New Zealand–North Korea relations (Korean:뉴질랜드-조선민주주의인민공화국 관계) refers to international relations between New Zealand and North Korea.  Relations between the two countries have been almost non-existent since the division of Korea.  During the Korean War in the 1950s, New Zealand troops fought as part of the United Nations force that repelled the North Korean invasion of South Korea.  Since then, New Zealand and North Korea have had little contact, until July 2000 when North Korean Foreign Minister Paek Nam-sun and New Zealand Minister of Foreign Affairs Phil Goff met in Bangkok, leading to the establishment of diplomatic relations in March 2001.  The New Zealand ambassador to South Korea based in Seoul is also cross-accredited to North Korea.  In 2006, North Korea tested its first nuclear weapon, drawing criticism and suspension of relations by the New Zealand government, which holds a staunch anti-nuclear policy.  New Zealand began re-establishing formal relations in 2007, when the New Zealand Minister of Foreign Affairs Winston Peters visited Pyongyang on November 20 to discuss possible political and economic deals with North Korea, on the basis that it start dismantling its nuclear weapons facilities.

Battle of Yongju: The Battle of Yongju (21–22 October 1950), also known as the Battle of the Apple Orchard, took place as part of the United Nations (UN) offensive towards the Yalu River, against the North Korean forces which had invaded South Korea during the Korean War.  The battle was fought between the 27th British Commonwealth Brigade and the North Korean 239th Regiment which was encircled east of Yongju, where it was attacking the US 187th Airborne Regimental Combat Team (US 187 RCT).  On 20 October US 187 RCT had parachuted ahead of the advancing UN spearheads into drop zones in Sukchon and Sunchon, 40 km north of the capital Pyongyang, with the objectives of cutting off the retreating North Korean forces that were withdrawing up the west coast of the Korean Peninsula and releasing American and South Korean prisoners of war.  Although the airborne drop itself was a success, the operation came too late to intercept any significant North Korean elements and the American landings initially met little resistance.  However, on 21 October as US 187 RCT began to advance south to the clear the Sukchon to Yongju road towards Pyongyang the Americans came under heavy attack from the North Korean 239th Regiment, and requested assistance.

United States in the Korean War: At the conclusion of World War II the Allied nations began the process of disarmament of Axis controlled regions.  Japan occupied Korea at this time and had been in control since 1910.  In 1945, the decision was made to have American Marines forces oversee Japanese surrender and disarmament south of the 38th parallel and the Soviet Union would facilitate the change of power to the north.  At the time there was no political motivation and seemed to be a logical and convenient plan of action.  The original agreement and intent was to create a unified and independent Korea out of the post Japanese occupation era.  Instead each side of the 38th parallel established its own government under the influence of the occupational country; the United States in South Korea and the Soviet Union in North Korea.  Both new Korean governments discredited the other and claimed to be the only legitimate political system.  Tensions between the North and South escalated and each side began to petition foreign powers for resources and support.  South Korea wanted weapons and supplies from Truman and the United States government while North Korea sought help from Stalin and the Soviet Union.  The United States was still war weary from the disruptive World War II campaign and refused South Korea's request for weapons and troops.  North Korea convinced the Soviet Union to supply them with the weapons and support they requested.  This decision coincided with the United States withdrawing the last remaining combat troops from South Korea.  North Korea saw its opportunity and attacked South Korean forces at the 38th parallel on June 25, 1950 and thus initiating the Korean War.

Korean War: The Korean War (in South Korean Hangul: 한국전쟁 ; Hanja: 韓國戰爭 ; RR: "Hanguk Jeonjaeng " , "Korean War"; in North Korean Chosŏn'gŭl: 조국해방전쟁 ; Hancha: 祖國解放戰爭 ; MR: "Choguk haebang chǒnjaeng " , "Fatherland Liberation War"; 25 June 1950 – 27 July 1953) was a war between North Korea (with the support of China and the Soviet Union) and South Korea (with the principal support of the United States).  The war began on 25 June 1950 when North Korea invaded South Korea.  The United Nations, with the United States as the principal force, came to the aid of South Korea.  China came to the aid of North Korea, and the Soviet Union also gave some assistance to the North.

December Massacres of 1950 in the Korean War: The December Massacres were a series of politically motivated executions carried out by the South Korean government following the recapture of Pyongyang by communist forces in the Korean War.  The killings took place mainly in and around Seoul but also in other locations in South Korea.  It is believed the South Korean government executed thousands of people though accurate estimates are difficult to come by.  The Rhee regime received criticism from the international community and the executions damaged his image.

Foreign relations of North Korea: The foreign relations of North Korea – officially the Democratic People's Republic of Korea (DPRK) – have been shaped by its conflict with capitalist countries like South Korea and its historical ties with world communism.  Both the government of the DPRK and the government of South Korea (officially the Republic of Korea) claim to be the government of the whole of Korea.  The Korean War in the 1950s failed to resolve the issue, leaving the DPRK locked in a military confrontation with South Korea and the United States Forces Korea across the Demilitarized Zone.  At the start of the Cold War, the DPRK only had diplomatic recognition by Communist countries.  Over the following decades, it established relations with developing countries and joined the Non-Aligned Movement.  When the Eastern Bloc collapsed in the years 1989–1991, the DPRK made efforts to improve its diplomatic relations with developed capitalist countries.  At the same time there were international efforts to resolve the confrontation on the Korean peninsula, especially when the North acquired nuclear weapons after the demise of the Soviet Union, its main economic backer.

Anti-American sentiment in Korea: The anti-American sentiment in Korea began with the earliest contact between the two nations and continued after the division of Korea.  In both North Korea and South Korea, anti-Americanism after the Korean War has focused on the presence and behavior of American military personnel (USFK), aggravated especially by high-profile accidents or crimes by U.S. service members, with various crimes including rape and assault, among others.  The 2002 Yangju highway incident especially ignited Anti-American passions.  The ongoing U.S. military presence in South Korea, especially at Yongsan Garrison (on a base previously used by the Imperial Japanese Army from 1910-1945) in central Seoul, remains a contentious issue.  However, 74% of South Koreans have a favorable view of the U.S., making South Korea one of the most pro-American countries in the world.

Battle of Pyongyang (1950): The Battle of Pyongyang (17–19 October 1950) was one of the major battles of the United Nations and South Korean offensive during the Korean War.  Following the Battle of Inchon, the UN forces recaptured Seoul, the capital of South Korea, and proceeded to north of the 38th parallel.  Shortly after advancing north, the American and South Korean forces faced the North Korean defensive near Pyongyang, the capital of North Korea, on October 17.  Since North Korea's leadership and its main forces had already withdrawn to Kanggye, the allied forces soon captured Pyongyang on October 19. The battle was followed by an airborne assault by the U.S. 187th Infantry Regiment 40km north of Pyongyang, with the intention of cutting off North Korean units retreating from the city.

Supporting paragraphs: Battle of Pyongyang (1950) Korean War
Answer: The United Nations, with the United States as the principal force