July 1950 was an exceedingly anxious time in America.

The country found itself very much on the defensive in the global struggle known as the Cold War. Over the preceding year, the Soviets had exploded their first atomic weapon, in effect erasing the West’s primary deterrent to Russian military adventurism in Europe.

In December 1949, Mao triumphed in his long struggle with the Chinese Nationalists, firm allies of the United States, and established the People’s Republic of China (PRC). All of a sudden, the most populous nation in the world had been “lost” to Communism, and the Republicans blamed the Truman administration for the debacle. Next door in Vietnam, Mao was supplying the Communist revolutionaries with vast quantities of military equipment and sound advice. Ho Chi Minh’s forces had seized the momentum in the war against their erstwhile colonial masters, the French.

President Truman in April 1950 had signed a top-secret directive, NSC-68, calling for the tripling of the U.S. defense budget, and vastly expanded aid to allies, in order to meet the challenge of Soviet expansionism. The Soviet Union, said the authors of the document, clearly intended “to impose its absolute authority over the rest of the world.”

Recent developments in Korea, where America was facing imminent military disaster, appeared to confirm the wisdom of NSC-68.

In the waning days of World War II, it had been agreed that the Russians would accept the Japanese surrender in northern Korea and occupy the peninsula north of the 38 th parallel, while the Americans would do the same to the south of that line. By 1948 a Communist regime under Kim Il Sung had emerged as a client state of the Soviet Union, while a pro-Western, authoritarian government under Singman Rhee ruled in south.

The two Korean regimes were locked in bitter conflict with one another from the outset. Both strongmen were committed to unifying Korea under their own administration, but only North Korea had the military assets to accomplish the task by force. The Russians had left behind ample supplies of tanks and heavy weapons. The Americans, fearing the irascible Rhee would invade North Korea and set off World War III, denied him the hardware he needed to undertake such an ambitious operation.

At 4 a.m. on June 25, Kim unleashed virtually his entire 135,000-man army in four powerful thrusts through the hills into South Korea. Spearheaded by an ample supply of T-34 tanks, the Korean People’s Army (KPA) buzz sawed through the Republic of Korea (ROK) border defenses and proceeded south at a brisk pace. Whole regiments of a very inept ROK Army—it was really more of a constabulary than a military force—disintegrated before North Korea’s armored juggernaut. Seoul, the South Korean capital, fell within three days, and the tanks kept rolling south.

Kim had gotten Stalin’s approval for his brazen offensive by convincing the Russian dictator that America would not intervene—after all, the U.S. had failed to save the Chinese Nationalists. Why would it bother to defend a country its own secretary of state had declared beyond the bounds of the American defense perimeter in Asia?

Kim was wrong. Truman, believing that Kim had attacked South Korea on Stalin’s orders, resolved to defend Rhee’s regime by every means at his disposal. He immediately sent naval and air forces toward the peninsula, and to the Taiwanese straits to protect the Nationalists on Formosa from what looked like an impending invasion by Mao’s People’s Liberation Army (PLA). The attack, said Truman, “makes it plain beyond all doubt that Communism has passed beyond the use of subversion to conquer independent nations and will now use armed invasion and war.” If South Korea were permitted to fall, the Soviets “would keep right on going and swallow up one piece of Asia after another.”

Thanks to a Soviet boycott of the UN for its refusal to give a seat to Mao’s new government, the United States pushed two resolutions through the Security Council. The first one condemned the North Korean invasion as a blatant act of aggression; the second called on member states to come to the aid of the South Koreans.

A military coalition of some 16 nations was formed in great haste. General Douglas MacArthur, whose Eighth Army was stationed in nearby Japan, was appointed Supreme Commander. The American Caesar immediately ordered elements of several woefully under-strength, ill-trained divisions of his occupation army into the faltering South Korean line. The Americans, soft from years of occupation duty and with absolutely no expectation of ever seeing combat, were no match against the Spartan KPA troops. Many KPA battalions had seen extensive action fighting for Mao in the Chinese Civil War.

Across the entire front for the month of July, U.S. and ROK units deserted their blocking positions and retreated ever farther south, behind one new defensive line and then another, even as American air and naval forces pounded away on KPA infantry-armor formations and supply lines.

August 1 found the North Koreans just 30 miles from the port of Pusan on the southeast coast, approaching the Naktong River. On the high ground south of the river, the battered UN ground forces (more than 90 percent were either American or ROK) faced a choice: they could hold their ground and fight, or conduct a humiliating withdrawal from Pusan to Japan. Urged on by commanding Gen. Walton Walker, a scrappy bulldog of a man, they dug in and fought.

By this point in the war, many of the incompetent and soft American officers and noncoms had been killed or relieved, and the Eighth Army contained within its ranks a tough cadre of regular soldiers with vast combat experience in World War II. Many had been hastily summoned from the reserves. These men steadied the nerves—and the performance—of the vast numbers of inexperienced enlisted men in their charge.

Over the next six weeks, the Eighth Army fended off a series of violent attacks against the 130-mile long perimeter, but it was a close-run thing. Without large numbers of last-minute reinforcements and superb air support, the perimeter would almost certainly have collapsed.

By September 5, the KPA had suffered 50,000 casualties and was running short of food and ammo. Morale was in the toilet. But this wasn’t at all clear to Gen. Walker or the American public, who feared their boys were on the point of great slaughter at the hands of Communist fanatics.

General MacArthur, however, took a more sanguine view. In early July, he had begun to conceive of a powerful amphibious landing deep in the enemy’s rear that would radically alter the balance of power on the peninsula. “The deep envelopment, based upon surprise, which severs the enemy’s supply lines, is and always has been the most decisive movement in war,” said the hero of the Philippines to skeptical members of his own staff.

MacArthur wanted the 1 st Marine Division to land at the port of Inchon, and fight its way east to recapture Seoul. Wresting the capital from the tough North Koreans would be a major psychological and political victory, but it was just the start of something bigger. He would trap the bulk of the KPA between the invasion force—X Corps—and the Eighth Army, and quickly destroy it.

Between early July and late August, the Joint Chiefs and all the senior commanders in the Pacific without exception expressed profound skepticism over MacArthur’s bold and risky concept, even as logistical preparations and planning proceeded apace. The more scarce resources flowed in the direction of the envelopment campaign, the greater the chance that the Eighth Army would collapse. Operation Chromite—the official name of the Inchon-Seoul campaign—was too distant from the Pusan perimeter for the two armies to support one another. The landing, it was said over and over again, would degenerate into another Anzio, with the UN force pinned to the beach by torrents of North Korean artillery fire.

Inchon’s 32-foot tidal range, opined the amphibious experts, meant that the big landing craft, the LSTs, would be stranded on the beach just a few hours after arrival. The channel leading to the port was so narrow it was sure to be well mined. If one ship went aground or was crippled by enemy fire in the channel, it would block the rest of the invasion force from reaching the beach.

Because of the peculiar tidal fluctuations, the main landing would have to take place in the late afternoon, leaving the Marines in the vanguard with only two hours to secure the lodgment. General Lemuel Shepherd, commander of the Fleet Marine Force in the Pacific, feared this was insufficient time to establish a beachhead against a defense force he expected to be as fanatical as the Japanese had been on Iwo Jima.

Remarkably, MacArthur never felt obliged to respond directly to these reservations and criticisms in any formal way. He simply pressed forward with planning for Chromite as if it had already been fully approved by the JCS and the president. “Against all the reasoned arguments of the admirals and generals,” writes historian Max Hastings, MacArthur “deployed only the rocklike, mystic certainty of his own instinct.”

At a decisive meeting in Tokyo between MacArthur, the Joint Chiefs, and the senior commanders in the Pacific on August 23, one officer after another expressed grave doubts over Chromite’s chances of success. Several alternative operations were discussed, including a landing much farther south at Kunsan, and a massive reinforcement of the Pusan perimeter, with a view to launching a conventional counter-offensive out of that enclave.

As the discussions went on, MacArthur sat serenely, puffing on his corncob pipe. Nothing seemed to shake his composure. And then, the UN’s Supreme Commander rose and began to pace the room. He spoke, said one Army officer in attendance, “with the slow, deep resonance of an accomplished actor.” The bulk of the KPA was committed to attacking the Eighth Army, at the end of tenuous supply lines running through Seoul. These could be easily cut by the Marines, for neither Inchon nor Seoul would be adequately defended.

“The North Koreans would regard an Inchon landing as impossible,” intoned America’s most regal general. “The very arguments presented here as to the impracticability involved will tend to ensure for me the element of surprise. My confidence in the Navy is complete. I seem to have more confidence in the Navy than the Navy has in itself …”

And then, after 45 spellbinding minutes without consulting a single note, he closed with a flourish: “I can almost hear the ticking of the second hand of destiny. We must act now or die … We shall land at Inchon, and I will crush them.”

Some in the room remained skeptical, but not many. MacArthur’s gravitas, coupled with his sterling record as a commander of amphibious operations in the Pacific, carried the day. Five days later, the JCS gave the green light to Operation Chromite.

It was to be a campaign of four phases: the assault on Inchon and the establishment of a secure lodgment; the drive on Seoul and its capture; the severing of the enemy’s lines of supply and communication; and, finally, the deployment of X Corps’ maneuver forces as an anvil against which the reinforced Eighth Army would hammer the trapped KPA divisions. D-Day was September 15.

It took four to five months to plan an amphibious operation the size of Chromite during World War II. The fact that only three weeks remained before D-Day meant that much would have to be left to chance and improvisation. Among the 260 ships assembled in the armada—pulled together from shipyards all over the world—were 30 World War II LSTs that had been converted to fishing boats by the Japanese. They weren’t even remotely combat-ready. Nor was there time for the Army and Marine units to conduct realistic amphibious training exercises. “The whole thing was a rusty travesty of a World War II amphibious operation,” exclaimed one Marine officer in the assault force.

But it worked. Brilliantly.

Of course, mistakes were made, but officers and men alike adapted and improvised, and luck smiled on the UN forces again and again as Chromite unfolded. The naval bombardment force easily cleared a small minefield in the narrow channel and went on to knock out virtually all the heavy guns on Wolmi Island, which protected Inchon harbor. The 3 rd Battalion of the 5 th Marine Regiment seized the island after about four hours of combat, taking only light casualties.

MacArthur had been right: Inchon was only lightly defended. The fast tides and limited visibility caused a number of the assault waves in the main invasion to land a fair distance from their objectives, but it didn’t matter much. By day’s end, 13,000 Marines were ashore, and the beachhead secure. Only 21 men had been killed.

It took ten days for the 1 st Marine Division to punch its way east to seize vital Kimpo Airfield and maneuver into the outskirts of the capital city. The fighting in Seoul was a nasty business—for three days and nights the infantry conducted an unremitting series of powerful assaults on enemy strongpoints, supported by tanks and air power. By the end of the first day, the whole city stank of cordite, napalm, sewage, and burning flesh.

By September 27, the Marines were clearing out the city’s main thoroughfare against fierce resistance. Staff Sgt. Lee Bergee recalled:

As we fought yard by yard up Ma-Po Boulevard, tanks led the way. I saw a North Korean soldier lying in the street. He’d been hit by … white phosphorous. His body was still burning. I watched one of the tanks roll over him, grinding his body into the pavement … At each barricade we had to annihilate the enemy, then reorganize, evacuate casualties, and go on to the next. At the railroad station we found the still-warm bodies of women and children massacred by the North Korean secret police.

At 3 p.m. on September 27, the stars and stripes replaced the North Korean flag atop the capitol building in downtown Seoul. Only the mopping up remained.

Having already taken heavy casualties in the fighting on the Pusan perimeter, the KPA, now numbering about 70,000 men, found itself in the unenviable position of being caught between two powerful UN armies. Low on ammunition, food, and morale, most KPA divisions disintegrated into roving bands soon after their initial encounter with UN forces, and tried desperately to make their way through the mountains back into North Korea.

The euphoria of victory, coupled with widespread outrage over the KPA’s savage treatment of civilians and POW’s alike, led President Truman and his senior advisers to seek a more ambitious objective than simply restoring the status quo antebellum. Now, MacArthur was duly authorized to conduct operations north of the 38 th parallel with a view to destroying Communist forces outright, and establishing UN control over North Korea … unless, of course, Mao or Stalin decided to intervene with their own armies.

On October 7, the Eighth Army advanced in high gear across the 38 th parallel. For a week, the KPA defenders put up spirited resistance, and then they vanished into the mountains. MacArthur’s forces plunged north as fast as they could, given the limits imposed by logistics and the primitive road network, ever closer to the Yalu River and the Chinese border.

The mood in Washington—indeed, in the entire nation—morphed from one of grinding doubt and worry to elation. Admiral Chester Nimitz, MacArthur’s great rival in the American drive across the Pacific in World War II, called Chromite “the most masterly and audacious strategic stroke in history.” That was stretching it a bit, but there was no denying that the war had been completely turned around, and fast.

A great many people contributed to the success of Chromite—the X Corps planning staff working in a pressure cooker environment; the Marines who conducted the assault so handily and seized Seoul; the Eighth Army, which had hung on by a thread for weeks and then shown its mettle in the breakout attack; the logistics officers who’d somehow managed to get the equipment and personnel to Japan on time to launch the invasion.

But all of these contributions, and others, were made possible by one man’s ingenious military insight, and his refusal to buckle when placed under enormous pressure to take a less risky tack. MacArthur’s brilliant and daring strategic vision, his coup d’oeil— was the key to success in Korea in the fall of 1950. Clausewitz, the great philosopher of war, defined coup d’oeil as “the commander’s ability to see things simply, to identify the whole business of war completely with himself, which is the essence of true generalship. Only if the mind works in this comprehensive fashion can it achieve the freedom it needs to dominate events and not be dominated by them.”

But Korea was above all else a war of nasty surprises, and coup d’oeil is a fleeting thing. As the first signs of winter began to appear on the bleak North Korean landscape in November, Mao Zedong ordered several hundred thousand Chinese People’s Army troops to cross the Yalu River and drive the UN armies back across the 38th parallel. This they did, leading to one of the most humiliating reversals of fortune in the history of American arms.

In December, with two UN (mostly American) armies in grim and harried retreat deep in North Korea, Truman and the JCS once again redefined their war objective. Now, they ordered MacArthur to stabilize the UN lines as far north as possible, so the UN command could seek a negotiated settlement. MacArthur, believing that “there was no substitute for victory,” desperately wanted massive reinforcements so he could go back on the offensive and invade China. When Truman refused to budge, MacArthur publicly accused the president of appeasement. An outraged Truman relieved the general of command on April 11. His 52-year military was over.

After two and a half more years of brutal combat along the 38 th parallel, an armistice brought an end to the fighting. The border between the two Korean governments was restored at the 38th parallel, but nothing of any real substance has been done since to resolve the implacable conflict between the West and North Korea. Sixty-four years after the armistice, the Korean peninsula remains a frightening vestige of the Cold War, and a bizarre and bellicose North Korean regime armed with nuclear weapons constitutes a dire and, in many ways, unprecedented threat to world peace, and to American national security.