The Korean War never really ended. That statement may sound like rhetorical overkill -a way of pointing out that the Korean peninsula remains a dangerous place, with North and South watching each other warily across their demilitarized zone. But it is, in fact, literally true. The armistice reached in 1953 called for weapons to be put down "until a final peaceful settlement is achieved." Yet no peace treaty ever followed. The first armed conflict of the Cold War is still under way, at least technically.

It is hardly unusual that we have overlooked this. The Korean War left few traces on the American popular memory. (Except via "M*A*S*H," which everybody knew was really about Vietnam anyway.) Getting beyond the stone wall of forgetfulness was David Halberstam's intent in writing The Coldest Winter, his final book, under revision when the author was killed in an automobile accident this spring.

"Korea," Halberstam writes, "would not prove a great national war of unifying singular purpose, as World War II had been, nor would it, like Vietnam a generation later, divide and thus haunt the nation. It was simply a puzzling, gray, very distant conflict, a war that went on and on and on, seemingly without hope or resolution, about which most Americans, save the men who fought there and their immediate families, preferred to know as little as possible."

Halberstam has enough respect for the integrity of his story not to burden it with frequent glosses on recent headlines from Iraq. The parallels are between the lines, yet hard to miss. At the same time, the events in Korea are echoes and answers to earlier moments. Describing an incident in the life of Douglas MacArthur's father that anticipated the general's showdown with President Harry Truman, Halberstam writes that it "would be an eerie kind of footnote to future events - history not so much repeating itself as preceding itself."

The book opens on a note of triumph, with American troops entering the North Korean capitol in the fall of 1950. The moment of glory soon reverses itself when a seemingly endless stream of Chinese troops arrives on the scene to back up their Korean comrades. (If the Americans called the conflict a "police action," Chairman Mao had his own euphemistic rhetoric: The Communist soldiers were all "volunteers.")

"Perhaps all wars are in some way or another the product of miscalculation," writes Halberstam. "But Korea was a place where almost every key decision on both sides turned on miscalculation." This is no exaggeration: Each party underestimated the strength and resolve of its opponents. At the same time, neither bloc in the conflict was quite as solid as it appeared.

Sending his army south, Kim Il Sung expected to be greeted as a hero. (He wasn't.) Stalin, misreading a diplomatic signal from Washington, thought the Americans would at least tolerate Kim's effort to unify the country by force. (They didn't.) And Gen. MacArthur - confident that he understood the workings of "the Oriental mind," was quite certain that the Chinese would stay out of the conflict. (So much for that.)

The North Korean incursion might have looked like international communism on the march. It came fast on the heels of Soviet expansion into Eastern Europe and the victory of Mao's revolution in China - not to mention the successful test of an atomic bomb that made Stalin's 70th birthday, in 1949, especially festive.

Drawing on recent historical research, Halberstam shows how much distrust and mutual contempt there was among the leaders of the Red camp. Ironically enough, the only American to have intuited this, it seems, was George Kennan - the diplomat and analyst who created the doctrine of containment. (Kennan has turned up in a number of Halberstam's books over the years, starting with The Best and the Brightest, always portrayed as one of the sharpest critical minds on the scene.)

But if the Communist bloc was not as monolithic as it appeared, neither was the American side of the conflict. A familiar truism had it that partisan disputes ended "at the water's edge" - as if, in Halberstam's words, "the foreign policy of the United States were some kind of sacrosanct area, separated from and placed above the normal meanness and conflicting interests of domestic constituencies and the passions they engendered."

The Korean War belied this fond delusion. The "passions," in this case, came largely from the Republican party, which had been out of the White House for almost two decades. Among its aggrieved elements were isolationists, the "China Lobby" (supporters of Chiang Kai-Shek), and Midwestern "paleoconservatives," as they might now be called. The latter were convinced that an Eastern establishment figure such as Dean Acheson was "soft on communism" even as he sought to triple the defense budget.

To these factions, MacArthur was not just a military hero. His defiance of Truman was obedience to God. Like any narrative historian, Halberstam's method leans heavily toward the biographical sketch; there must be dozens of them in The Coldest Winter. But it is the figure of MacArthur that looms largest - quite as the general himself would have expected, though hardly for the same reasons.

Perhaps only a man as grandiose as MacArthur could have conceived the landing at Inchon - a maneuver that, against unimaginable odds, drove back the North Koreans in the early months of the conflict. The certainty that he was a living embodiment of historical destiny had its downside, however. Ignoring the risk of a Chinese response led, in late 1950 and early '51, to the hellish ordeal alluded to in Halberstam's title.

He draws heavily on interviews with, and memoirs by, the American soldiers who fought in that seemingly endless season. They had to piece together an understanding of Chinese military doctrine when MacArthur's pontifications about "the Oriental mind" proved less than tactically adequate.

Undaunted, the general told friends at the Spanish and Portuguese embassies in Tokyo that he would soon take the war to China itself. Word of his plans reached Washington. The president yanked the chain of command, sending MacArthur back home to the states for a taste of civilian life.

The conflict ground on for more than two years longer: "a war of cruel, costly battles, of few breakthroughs, and of strategies designed to inflict maximum punishment on the other side without essentially changing the battle lines," as Halberstam writes. "In the end, there would be no great victory for anyone, only some kind of mutually unsatisfactory compromise." (History preceding itself, it seems.)

Like Halberstam's other work, The Coldest Winter is a bit shaggy at times. The prose can be repetitious. In some cases that seems appropriate - war itself is repetitious - though more often it just seems careless. The structure of the manuscript would have benefitted, at a few points, from the attentions of an editor with a strong hand. But then that is true of many a book by an author less gifted than Halberstam - and an editor up to the task is probably rarer than a general who could win the Battle of Inchon.