Nobody would dispute that Sen. John McCain marches to his own tune. The fife in his head starts fifing and the drum up there starts drumming and John McCain breaks camp, squints into the distance and marches off with confidence and vigor. He’s been around the block often enough to know that America’s rich diversity ensures somebody is always willing to follow.

The Arizona Republican is the kind of man who heeds the call to action. He served courageously in Vietnam. He has represented his state for 32 years in the House and Senate and he graciously humored tens of millions of Americans who thought no one was more suited than he to occupy the White House in 2008. He has delivered a steady stream of books to a grateful public.

A man doesn’t endure such hardship, scale such heights or find a publisher without possessing an insight or two into the hearts and minds of men. Maybe three insights. Tops. And insights into women, too. As long as the insight is something borrowed from others and repeated — again and again.

John McCain could have brooded over his thoughts for weeks or months or years and then quietly left it at that. But John McCain doesn’t brood or do things the quiet way. He doesn’t abandon the march because nobody else hears the music or because he doesn’t know where he wants to go or how to get there.

Grizzled litterateur that he also is, John McCain knows he’s got Mark Salter to scribble down the insights and put them into a new book: “13 Soldiers: A Personal History of Americans at War.” And John McCain would like the word, “scribble.” It conveys humility and John McCain is not only the kind of man who likes action, he’s also the kind who likes to convey humility while he’s being active. Who can forget his willingness to stand in the shadow of Sarah Palin in 2008? Or his inability to remember how many houses he owned?

John McCain knows from experience that nobody is a better comrade in the trenches of writing than Salter. The two combine the fog of war with the fog of writing. Salter has a vocabulary as rich as McCain’s insights.

They bring drill sergeant rigor to their subjects, shaping their 13 soldiers into a unit that includes “an intelligent spirited boy,” “a high-spirited and cheerful boy,” a “highly intelligent and decently educated” boy, “an excellent horseman and shot,” a man with “superior marksmanship and dignified bearing in the saddle” as well as “self confidence and social graces,” “a good-looking kid, athletic and popular with both sexes,” a “quiet boy  . . .  easygoing, quick with a joke, well liked and respected” and one “friendly and free with advice,” a “popular, good-looking kid,” a “typical outdoorsy kid from southern California, tough but fun-loving and good-natured.”

But John McCain and Salter understand that combat isn’t reserved for The Hardy Boys (with worryingly few good shots among them). Combat can ensnare The Little Rascals, too. In civilian life, John McCain and Salter’s less well behaved subjects “fought together, chased girls together, hopped freight trains and went on adventures together” or were a “little willful and given to misadventures for the fun of it.”

Historians can’t rule out that John McCain and Salter are here mixing up their notes from the 2008 campaign with their notes for this book, confusing the hijinks of the Palin family — Alaska’s First Brawlin’ Palin Regiment — with those of their 13 soldiers.

John McCain and Salter paint a picture in prose of soldierly simplicity. Picture John McCain, standing ramrod straight in Navy whites, flanked by a Connecticut Yankee, an African-American, a couple of Native Americans, “the fightingest little Chicano,” a landed Virginian, a Minnesota farm boy, a Pennsylvania suburban girl, a Boston Brahmin and others gazing moist-eyed into the middle distance. Smudge the picture a little because war is hell.

See a campaign commercial? Humble and self-disciplined man that he is, John McCain would go only so far as to hope so. The rest is up to you.

John McCain and Salter know that combat doesn’t always go according to plan. Neither does writing. Improvisation is essential. Another way to think of it is, making things up. If the historical record doesn’t exist, “we can imagine it  . . . ” McCain and Salter write. Or they can rely on a source who himself admitted to making it up.

John McCain and Salter aren’t deterred that their 13 soldiers aren’t always, er?, what’s the word? oh yes, participating, in the skirmishes they describe. They use this apparent weakness as a strength, giving readers an unsparing experience of military life: long bouts of boredom, the realization that crucial connections are being missed, the fear that the cause is hopeless and the nagging feeling that the people in charge are unquestionably nutty.