The Longest Day is extended to The Longest Year in “Band of Brothers,” a genuine television epic that painstakingly and indelibly charts the progress of a single U.S. Army company from before it parachuted into France on D-Day until after it captured Hitler’s Eagle’s Nest hideaway at the end of World War II. Exec produced by Tom Hanks and Steven Spielberg and very much influenced by “Saving Private Ryan” stylistically and in its unreservedly admiring stance toward the Greatest Generation, this gigantic work takes a while to marshal its forces — rather like the United States itself in the war, it might be said — but once it does, it becomes an imposing, vastly impressive powerhouse that will not be denied. Ten-part, $120 million adaptation of Stephen E. Ambrose’s bestseller will rivet war buffs with its exceptionally detailed and sharply focused look at the conflict from the point of view of men who were almost continuously in the line of fire for a year’s time. Still, the miniseries’ understated approach may not be everyone’s cup of tea, among them those HBO Sunday night regulars now accustomed to sensational dramatic hooks and outrageous surprises.

However much the now-elderly soldiers from the last Good War are celebrated for their bravery, heroism and selflessness in fighting fascism and saving the world for democracy, much of their appeal stems from their general refusal to buy into the hero worship. And it’s this low-key modesty and “just-doing-our-jobs” matter-of-factness that sets the tone for “Band of Brothers” and lends it such distinction. There are many issues and themes here, but when, at the end, the real-life Richard Winters — who, as impressively impersonated by Damian Lewis, emerges as the central figure of the piece — refuses the hero tag yet adds, “But I served in the company of heroes,” it’s exactly the right thematic grace note to underscore everything that’s gone before.

There have been many great war films, and any number that have vividly evoked the tension, tragedy and terror of battle. But due to the exceptional amount of time lavished on this story, the fluid manner in which men come and go and the drastic changes that mark them, it’s doubtful that any film or television venture has ever come close to “Brothers” in presenting the What-Men-Went-Through over the long haul.

If “Private Ryan,” in its first 25 minutes, plunged viewers into the intensity of battle in an unprecedented way, then “Brothers” has few, if any, rivals in conveying the sense of taking a village inch by inch, then having to do it all over again the next day, and the next, with good men being lost at every step of the way. That war is hell is easy to illustrate, but never has the overbearing, almost unendurable misery of weeks in a frozen, fogbound forest during the long standoff that was the Battle of the Bulge been portrayed with such evocative poetic realism and soundtrack silence.

“Band of Brothers” offers many rewards over the lengthy course of its dramatic and historical arc, but the first two episodes, which HBO has paired on opening night, are so familiar in subject and generalized in treatment that they pose a distinct threat to audiences deciding to make the long-term commitment. So indistinct are the dozens of faces that pass into frame, so slow is anyone to register with compelling interest, that the initial two hours come off like a live-action mural of typical WWII scenes: basic training (complete with a nasty commanding officer played with resolute meanness by David Schwimmer, the only “name” in the cast), tough drills, parachute practice, boring/anxious waiting around in England for D-Day to arrive and, finally, the invasion, which saw the men of Easy Company, 506th Regiment of the Army’s 101st Airborne Division, dropped into France in the wee hours before the beach landings. The visual sweep of dozens of planes and countless parachutes filling the night air is achieved through extensive CGI effects, and there are times, in Episode 2 especially, when one has the impression of watching an animated film. Installment even ends with a list of medals various soldiers received, a display of patriotic advertising that fortunately is not repeated.

Perhaps it’s not a coincidence that things start clicking when the fighting really starts getting heavy. Part 3 covers the progress of Easy Company through Normandy for several weeks after June 6, 1944, with particular concentration on the capture of the town of Carentan. Superbly adapting to the rugged, abrupt, verite style Spielberg and cinematographer Janusz Kaminski forged on “Private Ryan,” director Mikael Salomon (one of two helmers to have handled two episodes) and lenser Joel J. Ransom (who seamlessly split camera chores with Remi Adefarasin 50-50) pick their details carefully to create an impressionistic picture of foot soldiering heightened by graphic realism. Like “Ryan,” “Brothers” serves up an unusual amount of blood and gore; it becomes abundantly clear that the majority of battlefield bullets and explosions inflict painful injuries rather than clean kills.

Pic really hits its stride in its middle episodes. As the action moves from a failed incursion in Holland, where the Allies realized that breaking German resistance would be much more difficult than they imagined, to their unexpected, underequipped isolation in Bastogne, Belgium, during the frigid ’44 winter, and on through the Ardennes and finally into Germany, the physical and psychological toll on the men is starkly presented. Easy Company suffered an astounding 150% casualty rate, meaning replacements were constantly being shuffled in, and the uneasy relations between the eager newcomers and increasingly battle weary vets are notably highlighted.

That some officers were not up to leading men into battle is also underlined, as are the cravings for the spoils of war: Dead Germans’ Lugar pistols are highly prized by the grunts, and men are shown helping themselves to the treasures in Goering’s resplendent wine cellar and even to Hitler’s personal photo album.

Every episode begins with “Reds”-style living witnesses commenting upon a particular theme relevant to what’s about to unfold. But if there is a single, operating notion driving and unifying the 10 hours, it has to do with ordinary men rising to an extraordinary occasion. It’s for this reason, perhaps, that Winters, who began as a junior officer and rose to battalion executive officer, was chosen as the nominal central figure. Reserved, thoughtful, talented but hardly exceptional, unassuming but able to handle increasing authority, Winters perfectly embodies grace under pressure and modesty in the face of exceptional behavior. If the Greatest Generation needed a representative face, his is a good one (ironically, Lewis, the actor playing him, is British). Even then, however, his experience is put in relief by the trajectory of his closest friend from basic training, Lewis Nixon (Ron Livingston), a seemingly solid type who becomes increasingly unhinged, is demoted and by war’s end is single-mindedly interested in consuming as much of the best liquor he can find.

While the writers might well be participating in the creation of some fresh cliches, they deliberately avoid many of the stock elements of the Hollywood combat unit picture of yore; there is no attempt at societal melting pot representationalism, with guys of different ethnic and geographic background “colorfully” thrown together to symbolic or comic effect; backstory and psychology are all but eliminated, sparing us talk about wives, girlfriends and loved ones waiting on the home front; no puppy dogs are acquired en route; overt propaganda and flag-waving is mercifully minimal (ennoblement, beginning with Michael Kamen’s main theme music, is another matter); and “romance” is confined to some meaningful glances and exchanges with nurses (particularly well handled in Episode 5) and a handful of quickies (both thwarted and consummated) with local girls along the way. Writing in general is flavorful, smart and pared down, to the extent that the sounds of war tend to be as prominent as the dialogue.

Episode 9, entitled “Why We Fight” and underscored by the solemn strains of a Beethoven piece for string quartet, includes the company’s inadvertent discovery of a small concentration camp, a powerful episode conveyed under David Frankel’s direction with a steely gaze; keeping the perspective strictly to the personal level of the men, who have no clue what they have stumbled upon when they first see it, the dreadfulness of the place and the prisoners’ conditions is plainly rendered, without overstatement. What’s new, and devastating, is the sight of American soldiers rounding up the citizens of the nearby town and forcing these old German bourgeois, all dressed in their Sunday finest and disclaiming any knowledge of the camp, to bury the dead.

The fact of racial segregation in the armed forces is deftly dealt with in a single stroke, as a chance glimpse of a black soldier driving in a convoy is enough to remind those who haven’t realized it that only white faces have been on view up until now.

Part 10, mostly set in post-war Bavaria and Austria, rightly conveys a sense of winding down and looking ahead to individual futures, but there is tragedy and irony nonetheless, as well as the strong suggestion that there will be no way for these men to truly explain what they’ve been through to those back home. They have been fortunate to survive and are forever changed, unlikely to again experience anything nearly as profound in their lives.

Only a handful of characters, in a cast that includes 500 speaking roles, last from beginning to end; many are killed (more than a few without benefit of close-ups, making it impossible to reliably keep track of what’s happened to some of them), some recede, while others come to the fore. Some disappear only to pop up again unexpectedly, while replacements keep entering the picture, sometimes just for a moment and at other times to stick around for a while. One ends up feeling a great deal for the company as a whole, even if it’s hard to become terribly attached to individuals who, as likely as not, aren’t destined to last long.

Shot mostly on 1,100 acres of land around the former Hatfield Aerodrome near London, where much of “Private Ryan” was made, miniseries boasts outstanding verisimilitude in its wartime details as well as in the subtle differences in settings from country to country. Physically, it’s a tremendous achievement, with deep bows in order for production designer Anthony Pratt and his large team, costume designer Anna Sheppard, special effects supervisor Joss Williams, visual effects supervisors Angus Bickerton and Mat Beck, the cinematographers, editors, explosives experts, stunt crews, doubles, sound editors and on and on.

If “Band of Brothers,” title of which comes from the titular king’s rousing speech to his troops in Shakespeare’s “Henry V,” proves successful, perhaps another 10 hours will be forthcoming based on Ambrose’s next tome, “Citizen Soldiers of the Pacific,” a look at the U.S.’ other main theater of operations during the war.