Operation Chromite: MacArthur's Amphibious Strategy at Inchon

The Operational Environment at the Pusan Perimeter

The operational environment consisted of North Korean forces advancing toward the Pusan Perimeter so as to surround it. North Korea had just conquered Taejon and was moving in the direction of the UN's position, causing American and South Korean forces to retreat.

The dire situation facing the U.S. Eighth Army at the Pusan Perimeter was exacerbated by a steady decrease in strength that had continued since the conclusion of World War II: "Army forces consisted of four understrength divisions equipped with worn-out weapons from WWII."¹ The Army was using outdated weaponry, and the U.S. Eighth Army experienced logistical challenges due to the Korean landscape and air interdiction. Additionally, the Eighth Army was composed largely of young men who had never experienced combat, had little training, and possessed inadequate heavy artillery.²

General MacArthur's vision for Operation Chromite was to relieve NKPA pressure on the U.S. Eighth Army at the Pusan Perimeter by sending new units into the battle as they became available for action. MacArthur's use of amphibious and joint operations ensured that a complete defense and shift to offense could be conducted, placing the NKPA in a defensive rather than an offensive position. This in turn allowed the Eighth Army to prepare itself accordingly and set about reestablishing its position at the Perimeter.

MacArthur's Vision and End State

General MacArthur's vision for the operational environment once Operation Chromite was concluded—the end state—consisted of capturing Inchon and allowing UN forces to retake Seoul. The end state was thus characterized by the U.S. Eighth Army taking control of Inchon and supporting the UN takeover of Seoul. The four-point strategy employed to achieve this objective was to attack the rear of the NKPA and harm the enemy's supply lines to the south, while threatening the NKPA's capital at Pyongyang and leveraging political capital in the South by reasserting sovereignty in Seoul.

These four decisive actions were designed to send the message to the NKPA that it was futile to wage a conflict with the South, as this was tantamount to starting a conflict with the West—a conflict in which the NKPA stood no chance of prevailing. The bulk of the vision, however, rested on taking Inchon via amphibious assault as a joint operations exercise. This was the first step in the vision, as Inchon would serve as the base or foundation for the next step: the advance on Seoul and the severing of the enemy's lines of communication and supply.

The plan for Operation Chromite was to make use of amphibious assault to take Inchon: "The plan called for X Corps (to be formed around the 1st Marine Division and the 7th Infantry Division) to execute a phased amphibious landing at Inchon."³ The assault was planned and supported by joint operations, with Marines and air support available to assist in the landing. Once Inchon was taken, X Corps would head inland to take Seoul and cut the enemy's communications and supply lines that were sustaining the NKPA's forces in the south. JTF 7 was there to assist in the landing by providing support to secure the area surrounding Inchon, and the total effect of this joint operations approach was that the Eighth Army was completely supported.

Decisive Points and Joint Operations Planning

As JP-5 notes, a key decisive point is a major event or factor—such as a turning point in strategy—that allows one to obtain an advantage over one's enemy when enacted. As stated in the Joint Task Force Command and Control guide, "a commonly shared dynamic visual representation and associated Global Command and Control System (GCCS) data management tools can be used to integrate and manage relevant data sources," which will help a commander and his staff to identify decisive points.⁴

Two key decisive points for Operation Chromite were: (1) the use of asymmetric action—that is, the joint operations involving UN sea and air combat power directed at the land forces of the NKPA—and (2) MacArthur's vision, which included a clear expression of goals and the means by which those goals could be achieved. The first of these decisive points included understanding the vulnerabilities and weaknesses of the enemy and then planning a joint operations attack that would focus on that vulnerability. By exploiting the enemy's weakness, the U.S. was able to take what seemed like a strong offensive position to the NKPA and turn it into a weak, defensive one. Because the NKPA could not operate in the air and at sea as UN and U.S. forces could, it was at a significant disadvantage.

The second key decisive point involved MacArthur personally assessing the situation, drawing upon his past experience and knowledge to plan a decisive operation that would apply the strengths of Western forces against the weaknesses of the NKPA. By personally assessing the environment and understanding how joint operations could allow the UN and U.S. forces to turn the tables on the enemy, MacArthur established a clear vision by gaining a firm sense of the terrain and what was required. He then provided clear and coherent goals supported by a strategic course of operations that was both implementable and effective.