Atlanta was theirs. Now, it was time to make the rest of Georgia understand the consequences of war.

One hundred and fifty years ago Saturday, Union Gen. William Sherman left Atlanta, which had fallen two months earlier. He separated his army into two forces — one bound toward Macon, the other marching across the countryside toward Augusta. They comprised about 60,000 troops.

Before beginning a march to the sea, the general had a final order.

As the forces left Atlanta on Nov. 15, 1864, smoke rose behind them; it must have darkened the sun. In the downtown area, flames spread from one brick storefront to the next. “I believe,” one departing soldier said, “Sherman has set the very river on fire.”

Thus began the Burning of Atlanta. That episode in the 1861-65 war looms so large in our city history that it commands capital letters.

The event has helped define Atlanta. On our city seal is the phoenix, the mythical bird that rose from the ashes. Our motto: Resurgens, Latin for "rising again." It's burned in the memory of anyone who's seen "Gone With the Wind."

The destruction is memorialized in song, too. Famed guitarist Dickey Betts resurrected the episode in a 1978 recording of “Atlanta’s Burning Down.”

The conflagration also has been a topic of fiery debate: Just how much of our city did the Yankees really burn?

Local scholars figure the Union forces burned about 40 percent of Atlanta, the bulk of it in the business district on and around Peachtree Street. No one is sure of the full extent of the damage.

Truth, the saying goes, is the first casualty of war. Union witnesses reported about 25 percent of Atlanta was put to the torch; Confederate sympathizers placed the estimate much higher.

Some of the conflicting reports may stem from what happened before the flames, said Gordon Jones, a military historian at the Atlanta History Center. Atlanta, he said, had already taken a beating before any blue-clad invader reached for a torch.

“It wasn’t, all of a sudden, a bunch of guys just setting fire to the place,” he said.

In August, the federals began bombing the city. And Confederate Gen. John Bell Hood, before evacuating Atlanta on Sept. 1, destroyed supply depots so they wouldn’t fall into Union hands. He also ordered his troops to burn an ammo train, a conflagration that must have rocked the earth.

When it was Sherman’s turn to leave, the Union general borrowed the same page from Hood’s book: He ordered more facilities burned.

Stephen Davis, author of "What the Yankees Did to Us: Sherman's Bombardment and Wrecking of Atlanta," has visited spots in the city where factories and storefronts stood. His book is based on maps, photos and correspondence from witnesses to the destruction.

One correspondent, Atlantan Zachary Rice, visited the city days after Sherman and his minions had left. Much of Atlanta was still habitable, Rice concluded.

“He was saying, ‘The city is safe. Come on back,’” Davis said.

A young Atlanta girl offered a different perspective. Carrie Berry, who lived with her family in Atlanta, wrote a series of frightened entries in her diary during mid-November 1864. Renegade Union troops, she wrote, took out revenge on their unwilling hosts.

“Some mean soldiers set several houses on fire in different parts of the town,” she wrote on Nov. 12. “We all dread the next few days to come for they said that they would set the last house on fire if they had to leave this place.”

They did not live up to their threat. The Yankees left the Berry home intact.

They left the city in ruins, concluded Confederate W.P. Howard. He visited Atlanta on behalf of Georgia Gov. Joseph Brown to assess damage to state property. He didn’t stop at an inventory of state losses. Howard walked the city, counting destroyed homes and businesses.

The city, he determined, once had between 4,000 and 5,000 homes. Four hundred were left.

Turning his gaze to parks and homes just outside downtown, Howard made a dismal conclusion: “The suburbs,” he wrote to the governor in December 1864, “present to the eye one vast naked, ruined, deserted camp.”

Atlanta had no choice but to rebuild at war’s end, said Wendy Venet, a professor at Georgia State University who teaches classes in Civil War and 19th-century U.S. history. The city, whose population had more than doubled during the war, became a magnet for people wanting to make their postwar fortunes, she said.

“This town was run by, and populated by, people of great ambition,” she said. “There was money to be made.”

Still, resentment lingers. Davis, the author, recalls visiting a Civil War interest group, where one member pledged allegiance only to the Confederate flag. “The American flag,” he told Davis, “is a bloody, striped rag.”

Hard feelings, like mythical birds, are resurgens.