James Longstreet was the most loyal of Confederates. A Southerner, slave owner and second in command to Robert E. Lee, Longstreet, despite grave misgivings about Lee's strategy for the battle of Gettysburg, followed orders and led a charge that decimated the Confederate Army and destroyed Southern hopes.

But Longstreet had friends on both sides of the conflict, notably Ulysses S. Grant, Union Army commander and a fast friend since the two were cadets at West Point. While many Southerners reviled Grant as a butcher, Longstreet remembered a generous friend. When he swore an oath to the Union as a condition of his postwar freedom, his new loyalty was to the Union and to Grant, a decision that would turn Longstreet into "traitor number one" in the eyes of many Southerners, and dog him for the rest of his days.

In her new biography, acclaimed Civil War historian Elizabeth Varon does justice to this unlikely iconoclast. Varon looks beyond the war to Longstreet's travails during the blood-soaked years of Reconstruction, when his commitment to Congress' " revolutionary program for remaking the American South"was put to a severe test.

Longstreet's postwar life began in New Orleans. As a federal official, he worked with the Republican-controlled government and supported equal political rights for Black people, newly guaranteed by the 14th Amendment. A proven leader with an implacable air of authority, when Longstreet published four 1867 letters in various newspapers, he had a guaranteed readership but his forthright stance that the South should accept defeat inflamed Southern resentment. His war record was forgotten, then maligned. One paper said it would be better if Longstreet had died of his grievous war wound. Another compared him to one of Christ's murderers.

Meanwhile, in Louisiana, white supremacist terrorists "awash in a culture of paranoia and hatred" went on a rampage, committing over a thousand political murders in 1868 alone. In the middle of this combusting atmosphere, in 1872, Longstreet declared his support of a radical Republican gubernatorial ticket: a white governor, a Black lieutenant governor.

White rage exploded in the 1874 Battle of Liberty Place, when armed insurrectionists flooded the streets of New Orleans with the aim of throwing off federal control. Longstreet led a force of policemen and militiamen into battle against the so-called White League, but the insurrectionists briefly wrested power from the federal government. Wounded and held captive by the insurgents, Longstreet was eventually freed, but his life in New Orleans was over. His career in government service continued but his enemies never let up, widening their attacks to take aim at his war record.

The scapegoating of Longstreet tainted his reputation and, for decades afterwards, historians questioned his leadership. But in the 20th century, Longstreet's life story received recalibration and rehabilitation from novelist Michael Shaara, who read Longstreet's memoirs and made him the divided soul at the center of "The Killer Angels," his Pulitzer Prize-winning novel about Gettysburg.

Varon never quite gets to the core of Longstreet's gift (or curse) for thinking independently, but her brisk narrative style expertly sets his decisions into the context of the era. For readers interested in the tragedy of America's Civil War, the horrors of Reconstruction and their implications for our own divided time, "Longstreet" is an essential book.

Longstreet: The Confederate General Who Defied the South

By: Elizabeth R. Varon.

Publisher: Simon and Schuster, 516 pages, $35.