[2] DivInfo, HQMC, Biography of MajGen John T. Selden, Mar 54.
American concern in the 1950s for South Korea’s struggle to preserve its independence stemmed from a World War II agreement between the United States, the United Kingdom, and China. In December 1943, the three powers had signed the Cairo Declaration and bound themselves to ensure the freedom of the Korean people, then under the yoke of the Japanese Empire. At the Potsdam Conference, held on the outskirts of Berlin, Germany in July 1945, the United States, China,[3] and Britain renewed their Cairo promise.
[3] China did not attend. Instead, it received an advance copy of the proposed text. President Chiang Kai-shek signified Chinese approval on 26 July. A few hours later, the Potsdam Declaration was made public. Foreign Relations of the United States: The Conferences at Cairo and Teheran, 1943 (Department of State publication 7187), pp. 448–449; The Conference of Berlin (The Potsdam Conference), 1945, v. II (Department of State publication 7163), pp. 1278, 1282–1283, 1474–1476.
When the Soviet Union agreed to join forces against Japan, on 8 August, the USSR also became a party to the Cairo Declaration. According to terms of the Japanese capitulation on 11 August, the Soviets were to accept surrender of the defeated forces north of the 38th Parallel in Korea. South of that line, the commander of the American occupation forces would receive the surrender. The Russians wasted no time and on 12 August had their troops in northern Korea. American combat units, deployed throughout the Pacific, did not enter Korea until 8 September. Then they found the Soviet soldiers so firmly established they even refused to permit U.S. occupation officials from the south to cross over into the Russian sector. A December conference in Moscow led to a Russo-American commission to work out the postwar problems of Korean independence.
Meeting for the first time in March 1946, the commission was short-lived. Its failure, due to lack of Russian cooperation, paved the way for politico-military factions within the country that set up two separate Koreas. In the north the Communists, under Kim Il Sung, and in the south the Korean nationalists, led by Dr. Syngman Rhee, organized independent governments early in 1947. In May of that year, a second joint commission failed to unify the country. As a result the Korean problem was presented to the United Nations (UN). This postwar international agency was no more successful in resolving the differences between the disputing factions. It did, however, recognize the Rhee government in December 1948 as the representative one of the two dissident groups.
In June 1950, the North Koreans attempted to force unification of Korea under Communist control by crossing the 38th Parallel with seven infantry divisions heavily supported by artillery and tanks. Acting on a resolution presented by the United States, the United Nations responded by declaring the North Korean action a “breach of the peace” and called upon its members to assist the South Koreans in ousting the invaders. Many free countries around the globe offered their aid. In the United States, President Harry S. Truman authorized the use of U.S. air and naval units and, shortly thereafter, ground forces to evict the aggressors and restore the status quo. Under the command of General of the Army Douglas MacArthur, then Far East Commander, U.S. Eighth Army occupation troops in Japan embarked to South Korea.
The first combat unit sent from America to Korea was a Marine air-ground team, the 1st Provisional Marine Brigade, formed at Camp Pendleton, California on 7 July 1950, under Brigadier General Edward A. Craig. The same day the UN Security Council passed a resolution creating the United Nations Command (UNC) which was to exercise operational control over the international military forces rallying to the defense of South Korea. The Council asked the United States to appoint a commander of the UN forces; on the 8th, President Truman named his Far East Commander, General MacArthur, as Commander in Chief, United Nations Command (CinCUNC).
In Korea the Marines soon became known as the firemen of the Pusan Perimeter, for they were shifted from one trouble spot to the next all along the defensive ring around Pusan, the last United Nations stronghold in southeastern Korea during the early days of the fighting. A bold tactical stroke planned for mid-September was designed to relieve enemy pressure on Pusan and weaken the strength of the North Korean People’s Army (NKPA). As envisioned by General MacArthur, an amphibious landing at Inchon on the west coast, far to the enemy rear, would threaten the entire North Korean position south of the 38th Parallel. To help effect this coup, the UN Commander directed that the Marine brigade be pulled out of the Pusan area to take part in the landing at Inchon.
MacArthur’s assault force consisted of the 1st Marine Division, less one of its three regiments,[4] but including the 1st Korean Marine Corps (KMC) Regiment. Marine ground and aviation units were to assist in retaking Seoul, the South Korean capital, and to cut the supply line sustaining the NKPA divisions.
[4] The 7th Marines was on its way to Korea at the time of the Inchon landing. The brigade, however, joined the 1st Division at sea en route to the objective to provide elements of the 5th Regimental Combat Team (RCT).