Inchon, and Operational Maneuver From The Sea

The surprise North Korean invasion of South Korea steamrolled over lightly armed and poorly trained South Korean troops. Even the addition of US airpower and troop units did little to slow the onslaught. The defenders were soon pushed back to a small perimeter defending the port of Pusan. Pusan port was both their logistical lifeline, and presented the escape route should the perimeter fail.

But all was not lost. By the end of the summer of 1950, significant US troop units were available for commitment. Further, the North Korean army had stretched its lines of communication about as far as they could go.

Conventional military thinking called for the deployment of fresh forces into the Pusan perimeter, where eventually they could stage a counterattack, break out of the siege, and force the North Koreans back.

But a glance at the map would show that Korea is a peninsula. With the long shorelines on both coasts, North Korea had been forced to concentrate its ground forces at the Pusan perimeter, and its lines of communication were lightly defended.  These flanks were ripe for attack. And the commander of UN forces in Korea, General of the Army Douglas McArthur, was a past master of amphibious assaults, having used them brilliantly in World War II.  To our eyes some 60 year later, the choice to stage an amphibious assault seems easy.


The large scale demobilization of the services after World War II included a deliberate choice to mothball virtually all of the Navy’s amphibious warfare capability. The advent of nuclear weapons had convinced Navy planners (and Army planners as well) that any large scale amphibious landing would present a concentrated target tempting an enemy to use atomic weapons against it. A single atomic weapon would not only doom any landing, it would impose catastrophic losses of both shipping and manpower. And so the ability to land an expeditionary force against a defended coast had largely been foregone.

Further, while a brief glance at the map shows Korea as a peninsula, a detailed examination shows it to have some of the most inhospitable coasts, almost completely unsuitable for landings with the technology of the time.  Further, with the slashing of the US amphibious fleet, logistics over any assault beaches would be impossible. It’s one thing to land a force, it’s a far more difficult task to keep it supplied.

General MacArthur, after careful study, chose to conduct an amphibious assault, and chose the port of Inchon (which serves the South Korean capitol of Seoul) as the objective.  Located about halfway up the peninsula on the west coast, Inchon was lightly defended, and was a sufficiently deep envelopment that the North Korean army could not easily shift forces from Pusan to Inchon. But Inchon lies at the end of a long, notoriously treacherous channel with some of the worlds most complex tides. Further, rather than assaulting across open beaches, the troops would have to attack across a seawall onto open paved areas with little or no cover and concealment.

The Joint Chiefs of Staff had grave misgivings about the risks involved. Finding, mobilizing, training and deploying sufficient amphibious shipping and landing craft would be an enormous challenge, and the risks involved. If the Inchon channel was mined, or should the landing force otherwise falter, the invading force might be destroyed in detail.  The failure of any landing attempt would almost certainly cause support for our actions in Korea to collapse.

But the prospect of cutting off the North Koreans and destroying their invading army was tantalizing, and despite their doubts, the Joint Chiefs allowed the commander on the scene to follow his own course.

And so, on this day, September 15, in 1950, elements of the 1st Marine Division, with troops of the 7th Infantry Division in follow on waves, were landed by the US Navy at Inchon, in what is widely hailed as a strategic masterstroke, and one of the most decisive victories ever.

File:Battle of Inchon.png

The landings came as a strategic and tactical surprise to the North Koreans. With their lines of communication threatened, coupled with a breakout by UN forces in the Pusan perimeter, the North Korean army was soon fleeing South Korea in disarray. Had the landing forces at Inchon moved faster to retake Seoul, the North Koreans might have been trapped and destroyed. As it was, they barely managed to retreat not only from South Korea, but northward through their own country to the line of the Yalu River, where soon “volunteers” from the People’s Liberation Army of China would come to their rescue, and dashing hopes for any rapid victory and a lasting peace.

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First Lieutenant Baldomero Lopez, USMC, leads the 3rd Platoon, Company A, 1st Battalion, 5th Marines over the seawall on the northern side of Red Beach, as the second assault wave lands, 15 September 1950, during the Inchon invasion. Wooden scaling ladders are in use to facilitate disembarkation from the LCVP that brought these men to the shore. Lt. Lopez was killed in action within a few minutes, while assaulting a North Korean bunker. Note M-1 Carbine carried by Lt. Lopez, M-1 Rifles of other Marines and details of the Marines’ field gear. Photo number NH 96876. Image Courtesy of the Naval Historical Center.

Mastery of the seas and the ability to land forces upon hostile shores gives a ground commander a freedom of maneuver that allows him to choose the time and place of his assault, and usually provides him the opportunity to attack an undefended or lightly held position. The use of such maneuver to unhinge an enemy is a key to the operational art, whether it be the “Hail Mary” sweep to the west during Operation Desert Storm or the amphibious envelopment at Inchon in 1950.  Since that time, the US has been careful to maintain both the shipping and the expertise to allow it to conduct amphibious assaults worldwide.

7 thoughts on “Inchon, and Operational Maneuver From The Sea”

  1. Excellent article. General MacArthur was not only a military genius, he was a very lucky military genius. As you note, tides in the Flying Fish Channel leading to Inchon are complex; they are also quite high and low, with a more than thirty foot difference between high and low. Only rarely was the narrow channel deep enough to allow passage of Navy ships needed for an invasion.

    A tropical cyclone had passed the entrance to the Flying Fish channel shortly before September 15th — the date on which the invasion had to occur unless postponed until the following month, by which time the element of surprise would likely have been lost. Tropical cyclones are essentially intense low pressure areas. Having one of those at the entrance to the Flying Fish Channel on September 15th would have complicated the tides substantially, drawing water out of the channel and hence reducing the already minimal depths. An intense high pressure area over Inchon would have had a similar effect.

    Surprise was an essential element of the invasion. The DPRK did not expect an invasion at Inchon, due to the same problems feared by the Chiefs of Staff in Washington. In addition, General MacArthur staged feints at more “favorable” sites to the south and north of Inchon. The Inchon invasion came as a surprise and Inchon was lightly defended.

    General MacArthur probably was not overly concerned about mines in the channel, having dispatched an elderly Navy lieutenant, Eugene Clark, to survey the area. He evidently reported no mines there. Had there been mines, it seems unlikely that the invasion would have been attempted. Clearing the mines would have eliminated any element of surprise. Later, amphibious invasions on the East Coast were greatly delayed by the necessity to find and dispose of mines. The complex tides of the Flying Fish Channel were not involved there.

    Unfortunately, General MacArthur relied heavily on General Willoughby, his G2 and a member of the “Bataan Gang,” who sought and found favor by giving him only the information he thought was desired. As ROK and US/UN forces moved north and approached the border with China, China intervened massively and pushed our forces into a disastrous retreat. There had been information suggesting that Chinese forces would enter the fight in substantial numbers were its border approached but that information was rejected, apparently because inconsistent with General MacArthur’s perceptions. And that was the beginning of the end for General MacArthur.

    1. My understanding is that Willoughby did report some captures of Chinese troops, and started asking questions, particularly of outside intel sources in Washington, but got no replies. They were genuinely caught flatfooted, but most of the blame on that lies in DC. Not all, but most. William Manchester, who hated MacArthur, placed most of the blame there as well. As we later found, there were Red moles in DC who were withholding info. Additionally, Acheson’s gang got things set up so that all of Mac’s moves had to be approved in advance and we later found the moles were passing his plans onto the Reds.

      I fault Mac for not watching how Walker was advancing which allowed the Chinks to infiltrate and hide in the mountains until they had built up enough to actually hit 8th Army. By the time Mac knew what was going on, and had planned to relieve Walker, Walker was killed in a Jeep accident. For his troubles, Walker got a hotel named after him at the Berchtesgaden US Recreation Center in Germany, which was recently demolished by the Bavarian Government.

  2. Inchon was a masterstroke. One story I had only hear vaguely was our CIA/Navy recon effort.

    However, North Korean Army remnants escaped envelopment. The reason the trap did not work was the slow advance and fierce fighting in and around Seoul. Seoul was recaptured at great cost to the front-line Marine strength. This focus on a capital vice the enemy forces is similar to Mark Clark’s error in taking Rome in 1944, vice cutting off the German forces.

    The Inchon scenario was my favorte in SSG’s old Battlefront system. Very difficult for the UN to win.

  3. There was no ‘Hail Mary Sweep’ to the west in Operation Desert Storm. Bart Starr of Green Bay Packers ‘Snow Bowl’ fame saw that the maps Gen. Schwartzkopf was showing during his lectures were showing a ‘Sweep 49 Lombardi,’ and wrote a letter to that effect to the General. Schwartzkopf wrote back saying that Starr was correct – When the general was a cadet playing football at West Point, guess who was assistant coach? Vince Lombardi. The entire story is in American Heritage magazine.

    1. You’re correct, of course. And the wide envelopment to the west was not a move of desperation, but a carefully planned move to trap the IRGC. But it was described as the “Hail Mary” in the media, and thus I refer to it as such, not because it is an accurate description, but because it easily identifies to the reader which maneuver in Desert Storm I’m talking about.

      If you could find a link to that American Heritage story, that would be a hoot. Thanks for delurking!

  4. Brad,

    Was getting windshield time when you posted this. Great article. OMFTS is and will remain an essential element of our STRATEGIC maneuver for the foreseeable future, as it has been a part of warfare since antiquity.

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