How is it that Americans tuned into “M*A*S*H” for 11 years - savoring a mighty impressive 250-plus episodes - and yet the Korean War remains “The Forgotten War”? The answer may be that while “M*A*S*H” reminded us that war is hell, anything that comes with a laugh track is likely to dial down the violence, evisceration and sheer terror that accompany battle. Moreover, “M*A*S*H” was a general anti-war statement, not an attempt to illuminate the specific “police action” that was sandwiched between World War II and the Vietnam War.

Over the past few years, however, it has seemed to me that Korea is finally being remembered for the three-year nightmare it was. Recently, I’ve read histories of the conflict by David Halberstam (“The Coldest Winter”) and Bruce Cumings (“The Korean War: A History”), as well as Jayne Anne Phillips’ novel “Lark & Termite” – a National Book Award finalist in 2009.

Nobel laureate Toni Morrison has just published “Home,” a novel about a Korean War veteran.

And this month Robert Olmstead turns his prose – gritty one moment, lyrical the next – on the conflict in his book, “The Coldest Night.” Fans of Olmstead’s Civil War novel, “Coal Black Horse,” of which I am one, will not be disappointed. “The Coldest Night” is riveting, thoughtful and – in the large section set in Korea – harrowing.

The novel is the story of young Henry Childs, a high school junior happily playing baseball and working at a stable in West Virginia in 1950. There he and a high school senior named Mercy, a gifted rider and the daughter of a local judge, begin a doomed romance.

Mercy comes from money and power, while Henry is a child of the hill country who hasn’t even a clue who his father is. The first third of the novel chronicles their decision to run away together to New Orleans and hope that true love – and staggering amounts of sex – can bridge the social chasm that separates them.

When Mercy’s family intervenes, Henry, though underage, joins the Marines and sets off for Korea, where the second third of the novel is set.

Here, in the brutal cold and relentless carnage of the Battle of the Chosin Reservoir, the young man fights off an endless stream of North Korean charges before finally beginning the long retreat to the sea with his mentor, a hardened veteran.

Olmstead is an immensely gifted stylist, his prose capable of conveying the magic and passion of first love as well as the ferocity of battle.

He also has a knack for imagery as memorable as it is unexpected, such as what might have been a moment of calm between enemy attacks:

“A marine with a flamethrower walked the ridge methodically dispatching the enemy wounded. He lashed out with roaring flames thirty feet long, burning to death anyone of them that still moved and each time was the splattering noise of napalm liquid from the nozzle fire and a cloud of black smoke. He did not stop until his tanks were empty.”

I cared deeply about Mercy and Henry and his fellow soldiers, and the book moves at a spectacularly rapid clip – especially that middle third.

But “The Coldest Night” is not subtle. Exhibit A: It is a coming-of-age novel about a young man named “Childs.” Exhibit B: It is a picaresque with epigraphs for the three parts from, respectively, the Book of Job, “The Iliad” and “The Odyssey.”

Moreover, as much as I appreciated Mercy as a character, sometimes she seems more adolescent male fantasy than flesh-and-blood teenage girl. “You opened my body and took out all my bones starting with the small ones,” she whispers to Henry in one moment of post-coital tenderness.

Finally, the novel occasionally felt to me a bit too close to “Coal Black Horse.” Instead of a young man losing his innocence amid the summer maelstrom of Gettysburg, he loses it in the frigid killing fields of Korea.

But maybe that’s a ridiculous objection. After all, novelists play to their strengths. And few write as powerfully or as realistically as Olmstead about the way war makes a boy grow up far too fast.