Webster’s Collegiate Dictionary defines the word “indispensable” as “1: not subject to being set aside or neglected, 2: absolutely necessary.” Walter Stahr’s sweeping and much-needed new biography of William Henry Seward places the life of Seward deeply within the parameters of Webster’s definition. In straightforward and honest prose, Stahr ably argues that Seward was not only indispensable to President Abraham Lincoln as his secretary of state during the Civil War but was indispensable to the nation as well.

The last full biography of Seward appeared four decades ago. Since then, much new ground has been mined about American history during the middle part of the 19th century, and about the Civil War in particular. Delving deeply into a myriad of archival research and current historical interpretation, Stahr lifts Seward to his rightful place in the pantheon of, for lack of better words, “second-tier players” of American history. More and more, biographical literature is focusing on people who played a significant role in American life but have been overshadowed by the likes of Lincoln, George Washington and Thomas Jefferson. This supporting cast is now getting its due, and it is about time.

Shortly before Seward’s death in 1873, the Daily Alta California summed up Seward’s career and life, arguing that “he has stamped his name indelibly upon the records of time, and upon the geography of his country, while too many of our presidents have been mere tallies by which the nation may vaguely determine its age.” Most Americans probably have heard Seward’s name connected with his famous purchase of Alaska, the notorious “Seward’s Folly.” Others may have an inkling of the role Seward played in Lincoln’s wartime Cabinet. In either case, most Americans do not “know” the man. With this biography they now can.

Stahr’s biography is not hagiography. He claims that “Seward was not a saint, he was a practical politician, and he was prepared if necessary to use dubious means to achieve great goals,” the shady financing of the purchase of Alaska in particular. Stahr’s approach is balanced, but at times he gives away his overriding sentiment that he likes his subject. Readers will, too.

The portrait laid out is that of a man, born in 1801, who came to age during the formative years of the Republic. By the time Seward was 20 he was active in New York state politics, and when elected governor in 1838 he was one of its youngest. Drawn to the Whig ideology of protective tariffs, a national bank, internal improvements and national expansion, Seward became a rising star in that party. He was unusual in that during an age that feared immigrants and Roman Catholics, he, a Protestant, became their champion, arguing that including them in the national fabric would add to the nation writ large. When it came to African Americans, Seward, who opposed slavery but was no abolitionist, was more ambivalent and cagey, and he carried that attitude with him into the Lincoln administration. Here was a man who aided Harriet Tubman in purchasing a house in Auburn, N.Y., his hometown, but who also argued that the issue of civil rights for the newly freed slaves of the South should be adjudicated by the southern states, not the national government.

The rough and tumble of mid-19th-century American politics was not for the faint of heart. On the eve of the Republican National Convention in 1860 (the Republican Party was a new political party carved out of free soil, free labor men and former Whigs), Seward was the hands-down favorite to secure the nomination. In reality he had earned it; he had worked hard to secure Whig agendas when that party was relevant and embraced the Republican platform of limiting the extension of slavery, avoiding the issue of slavery where it existed. Shrewdly outmaneuvered at the Chicago convention by Lincoln supporters, Seward lost on the third ballot.

Deeply disappointed but not bitter, Seward agreed to serve as Lincoln’s secretary of state. For Seward, the life of the Union was more important than personal ambition. The initial relationship between Lincoln and Seward was rocky, but once Lincoln let Seward know who was “boss,” they became good friends. Recognizing his limited expertise in foreign policy, Lincoln let Seward, with much experience in that area from his days in the U.S. Senate, run the State Department. Seward was a fortuitous choice, for he worked hard to keep England and France neutral during the Civil War.

During what the author calls “the Cuban Missile Crisis of the 19th century,” the Trent affair, Lincoln followed Seward’s lead as the United States and England almost came to blows when an overzealous American naval commander plucked two Confederate emissaries to Great Britain from an English merchant ship. The Trent affair was the most serious foreign policy crisis the North endured during the Civil War. But there were numerous other diplomatic brushfires with which Seward had to contend, and his cool, calm and collected nature steadily guided the North, even as his fellow Cabinet members, often jealous, conspired against him.

An air of personal indifference about appearance and dress led others to believe that Seward was lazy, uncouth and indifferent to anything but his own ambitions. Nothing could be further from the truth, as this politician’s politician understood well how best to play the game while remaining his own man. With a drink in one hand, a cigar in the other and always willing to chitchat with whoever was at hand — be they writers, actors, other politicos or generals — while keeping a keen eye on a problematic world, Seward remains a colorful figure against a dark backdrop. A close acquaintance of Seward once said that he was “kind, genial, approachable and humorous — full of good points, diplomatic to a fault.” So too is this biography.

James A. Percoco is the director of education for the National WW II Memorial and a member of the National Teachers Hall of Fame.