THE IMMORTAL IRISHMAN:The Irish Revolutionary Who Became an American Hero

By Timothy Egan. Houghton Mifflin Harcourt, 368 pp., illustrated, $28

From the famine-wracked shores of Ireland, where he helped to foment rebellion, to the faraway penal colony of Tasmania, where he defied his life sentence by escaping, to the divided nation of Civil War America, where he continued his lifelong battle for freedom, he strutted, struggled, and survived. He was Thomas Francis Meagher, the greatest hero, adventurer, rebel, dreamer, and combatant you may never have heard of — but, whom, thanks to Timothy Egan, you will never forget.

“He had lived a dozen lives in his two score and three — lived an abundance of horror and no small number of triumphs,’’ Egan writes. “But more than that, he’d shaped his times.’’

“The Immortal Irishman’’ is an old-fashioned tale of tall talk, high ideals, and irresistible appeal. It is the story of a Waterford man, born in 1823, of crystal-eyed passion and indomitable will. He knew Abraham Lincoln and Daniel O’Connor but was a liberator (of prisoners in the South Pacific and of blacks in America’s South) in his own right — an irrepressible battler for rights and for what was, by his lights, right. You will not read a historical thriller like this all year.

The central theme is the evolution and endurance of the Irish spirit, brutalized by the British, by the potato famine, by the long passage to the new opportunities of the New World, but never defeated. Egan notes that in occupied Ireland, a land of powerlessness, penury, and the Penal Laws, it was illegal for “a piper, story-teller, babler, or rimer’’ to be in the company of an Englishman. Egan is, in his occasional rhetorical excesses, a bit of a “babler,’’ but above all he is a master storyteller.

Meagher was a born rebel. He bridled against the restrictions of occupation, thinking that his own people were “like blind and crippled children, in the dark.’’ All this came into sharp relief when he was sent by his relatively well-to-do merchant-class family to England for a posh schooling. But it didn’t take. “The life felt fake,’’ Egan says, “treading in mediocrity while his country fell into a torpor.’’

Meagher’s heart beat to the rhythms of Irish verse, that of Thomas Davis, the “bard of Young Ireland,’’ especially. Before long Meagher was speaking of England as “mean, unjust, contemptuous.’’ Amid the uprising of Ireland’s young during the famine he became known as a leader, the “Young Tribune.’’ He bellowed in one speech: “The people will not consent to live another year in a graveyard!’’

Charged with, and jailed for, his anti-British agitation, Meagher faced hanging, decapitation, and quartering — a kind of trifecta of punishment, though his sentence eventually was committed to “transportation for life’’ at age 26 to Tasmania, 112 days away by brig. Tasmania was, in his words, “a raw-ill-formed colony . . . teeming with all the vulgarities of English life.’’ A daring and dangerous escape delivered him to America and the New York of 1852, its soundtrack the music of refugees and castoffs from other tragic lands — “the poorest and most wretched population that can be found in the world,’’ according to the city’s Catholic archbishop.

A repository of famine Irish hopes in America even as he was the target of Know-Nothing nativist propaganda, Meagher turned his attention to issues dividing his new land. His next incarnation was as the Civil War leader of the famous Irish Brigade, emerging as what Egan characterizes as “a traveling rally-igniter for the Union cause.’’

But the Meagher saga doesn’t end at Bull Run or Fredericksburg. After the war President Andrew Johnson appointed him secretary of Montana, the wild territory’s second-ranking official.

“As one of the primary architects assigned to organize the foundations of government and civilization in a rawboned land,’’ Egan writes, “Meagher would be fortune-seeking as well as nation-building.’’ There the man who once set himself as a rebel fought the rebellious vigilantes who ranged through the territory.

Like his life, his end was one of high drama, presumably coming after a tumble off a steamboat into the Missouri River. His remains were never found, and his disappearance sparked a rash of rumors, including that he was murdered, had committed suicide, or simply stumbled overboard in a drunken stupor.

A century later John F. Kennedy traveled to Ireland and saluted Meagher, saying that the “quality of the Irish’’ was “the remarkable combination of hope, confidence and imagination’’ that he personified. The president of the United States had brought with him to his ancestral homeland a flag from Meagher’s Irish Brigade. It was proof that Meagher was, as Egan’s title describes him, an immortal Irishman.

David M. Shribman, for a decade the Globe’s Washington bureau chief, is executive editor of the Pittsburgh Post-Gazette. He can be reached at dshribman@post-gazette.com.