Question: What person ordered caution at the Sino-Korean border?
About the article "Korean War", section "UN forces cross partition line (September – October 1950)".

Candidate passages:
UN forces cross partition line (September – October 1950).
On 27 September, MacArthur received the top secret National Security Council Memorandum 81/1 from Truman reminding him that operations north of the 38th parallel were authorized only if "at the time of such operation there was no entry into North Korea by major Soviet or Chinese Communist forces, no announcements of intended entry, nor a threat to counter our operations militarily..." On 29 September MacArthur restored the government of the Republic of Korea under Syngman Rhee.
On 30 September, Defense Secretary George Marshall sent an eyes-only message to MacArthur: "We want you to feel unhampered tactically and strategically to proceed north of the 38th parallel."
During October, the ROK police executed people who were suspected to be sympathetic to North Korea, and similar massacres were carried out until early 1951.
On 30 September, Zhou Enlai warned the U.S. that China was prepared to intervene in Korea if the U.S. crossed the 38th parallel.
Zhou attempted to advise North Korean commanders on how to conduct a general withdrawal by using the same tactics which had allowed Chinese communist forces to successfully escape Chiang Kai-shek's Encirclement Campaigns in the 1930s, but by some accounts North Korean commanders did not utilize these tactics effectively.
Bruce Cumings argues, however, the KPA's rapid withdrawal was strategic, with troops melting into the mountains from where they could launch guerrilla raids on the UN forces spread out on the coasts.
By 1 October 1950, the UN Command repelled the KPA northwards past the 38th parallel; the ROK Army crossed after them, into North Korea.
MacArthur made a statement demanding the KPA's unconditional surrender.
Six days later, on 7 October, with UN authorization, the UN Command forces followed the ROK forces northwards.
The X Corps landed at Wonsan (in southeastern North Korea) and Riwon (in northeastern North Korea), already captured by ROK forces.
The Eighth U.S. Army and the ROK Army drove up western Korea and captured Pyongyang city, the North Korean capital, on 19 October 1950.
The 187th Airborne Regimental Combat Team ("Rakkasans") made their first of two combat jumps during the Korean War on 20 October 1950 at Sunchon and Sukchon.
The missions of the 187th were to cut the road north going to China, preventing North Korean leaders from escaping from Pyongyang; and to rescue American prisoners of war.
At month's end, UN forces held 135,000 KPA prisoners of war.
Taking advantage of the UN Command's strategic momentum against the communists, General MacArthur believed it necessary to extend the Korean War into China to destroy depots supplying the North Korean war effort.
President Truman disagreed, and ordered caution at the Sino-Korean border.
 1,950 C.E.
— 1,991 C.E.
Cold War *1,950 C.E.
— 1,953 C.E.
Korean War *1,969 C.E.
Sino–Soviet border conflict *1,967 C.E.
Chola incident *1,962 C.E.
Sino-Indian War *1,964 C.E.
Battle of the Paracel Islands *1,979 C.E., 1,984 C.E.
Sino-Vietnamese War *1,987 C.E.
1987 Sino-Indian skirmish *1,988 C.E.
Johnson South Reef Skirmish  
The history of Sino-Korean relations dates back to prehistoric times. 
The Korean War began in June 1950 with the Korean People's Army (KPA) of the north attacking the Republic of Korea in the south.
The invasion was almost successful in conquering all of the Republic of Korea until the United Nations (UN) intervened, sending ground forces into the country under the command of the United States.
The UN forces initially experienced early defeats until the Battle of the Pusan Perimeter, where the UN forces reversed North Korea's momentum.
By October 1950, the KPA was effectively destroyed by the UN forces after the landing at Inchon.
Despite the strong objections from the People's Republic of China on North Korea's northern border, the US Eighth Army crossed the 38th parallel and advanced towards the Sino-Korean border at the Yalu River.
As part of the Thanksgiving Offensive to end the war, the Republic of Korea (ROK) II Corps, which was composed of the ROK 6th, 7th and 8th Infantry Division, was ordered to attack north towards the Yalu River through the village of Onjong on October 23, 1950.
In response to the UN advances, China's Chairman, Mao Zedong, ordered the People's Liberation Army's North East Frontier Force to enter North Korea and engage UN forces under the name People's Volunteer Army (PVA).
In order to stabilize the rapidly collapsing Korean front and to push back the advancing UN forces, Mao authorized the First Phase Campaign, a bridgehead-building operation with the aim of destroying the ROK II Corps, the vanguard and the right flank of the US Eighth Army, advancing up the along the Taebaek Mountains in the middle of the peninsula.
After the Chinese leadership finally settled the issue of armed intervention on October 18, Mao ordered the PVA to enter Korea on October 19 under strict secrecy. 
Sino-Korean words are derived from literary Chinese as well as some from Sino-Japanese.
Some Sino-Korean words derive from Japanese "kun'yomi" words, that is, native Japanese words written in Chinese characters.
When borrowed into Korean, the characters are given Sino-Korean pronunciations.
(Note that in Japanese, these words are not considered to belong to the Sino-Japanese part of the vocabulary as they are native Japanese words.)