The UN, in its 7 July resolution, having authorized the United States to form a unified military force and appoint a supreme commander in Korea, it fell upon the Administration of President Harry S. Truman to translate this dictum into workaday reality. Aiding the Chief Executive and his Cabinet in this delicate task with its far-reaching implications were the Joint U. S. Chiefs of Staff (JCS). The Army member, General J. Lawton Collins, also functioned as Executive Agent of JCS for the United Nations Command in Korea, thus keeping intact the usual chain of command from the Army Chief of Staff to General MacArthur, who now served both the U. S. and UN.[5]
[5] Maj J. F. Schnabel, USA, Comments on preliminary manuscript (Comments).
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Late in August, two of the Joint Chiefs, General Collins and Admiral Forrest P. Sherman, USN, had flown to Japan to discuss the forthcoming Inchon landing with General MacArthur. In the course of the talks, it was agreed that CinCUNC’s objective should be the destruction of the North Korean forces, and that ground operations should be extended beyond the 38th Parallel to achieve this goal. The agreement took the form of a recommendation, placed before Secretary of Defense Louis Johnson on 7 September.[6]
[6] JCS memo to Secretary of Defense (SecDef), 7 Sep 50. Unless otherwise stated, copies of all messages cited are on file in Historical Branch, HQMC.
A week later, JCS informed MacArthur that President Truman had approved certain “conclusions” relating to the Korean conflict, but that these were not yet to be construed as final decisions. Among other things, the Chief Executive accepted the reasoning that UN Forces had a legal basis for engaging the NKPA north of the Parallel. MacArthur would plan operations accordingly, JCS directed, but would carry them out only after being granted explicit permission.[7]
[7] JCS message (msg) WAR 91680, 15 Sep 50; Harry S. Truman, Memoirs, 2 vols (Garden City, 1955–1956), II, 359.
The historic authorization, based on recommendations of the National Security Council to President Truman, reached General Headquarters (GHQ), Tokyo, in a message dispatched by JCS on 27 September: