As he researched the first volume of his planned American Revolution trilogy, Rick Atkinson traveled from the battlefields of Massachusetts to London's Windsor Castle, where he looked through the papers of King George III.

"I was there for a month and every day would show my badge at Henry VIII Gate, and climb the Round Tower," he told The Associated Press during a recent telephone interview. "And there are the papers. It's a very tactile sense of being in George's presence."

Atkinson's "The British are Coming" (Henry Holt & Co.) is his ninth book, and his first since completing his acclaimed "Liberation Trilogy" on World War II. He was a two-time Pulitzer Prize winner for The Washington Post and also won a Pulitzer in 2003 for the first of his World War II histories, "An Army at Dawn: The War in North Africa, 1942-1943." He has been praised for combining deep research with a vivid writing style.

"The British are Coming," published this week, adds to a surprisingly thin genre: a multivolume work centered on the Revolutionary War itself. Countless books have been written on the founders, and multivolume biographies date back to the early years of the country: John Marshall, the Supreme Court chief justice, wrote five volumes on George Washington that came out in the early 1800s. But the most acclaimed books on the Revolutionary War have been single-volume publications extending beyond the British surrender, from Robert Middlekauff's "The Glorious Cause" to John Ferling's "A Leap in the Dark."

"Most people think of the revolution as just a series of well-known battles," says Nathaniel Philbrick, whose books include "Bunker Hill" and "In the Hurricane's Eye," which covers the war's conclusion. "They know about Lexington and Concord, and somehow things get to Valley Forge, then other stuff happens and the British surrender at Yorktown. But of course it didn't happen that way and I don't see a lot of multivolume treatments on it."

Ray Raphael, author of "Founders" and "A People's History of the American Revolution," said it was "standard wisdom" in publishing that Civil War books are more popular and more likely to inspire ambitious projects.

And Atkinson acknowledges that the Revolutionary War, a means to separate from the English rather than a desire for conquest, differed from World War II "in magnitude, breadth, and consequence. "

"One was a global conflagration that left 60 million dead, the other was an obscure insurgency on the edge of the world," he says. "But in fact I find that as a writer, war is war. The struggle for survival, the fear, the exhaustion, the boredom, the utter misery, the loneliness — all are really of a piece when it comes to combat. The mystical bond between leaders and led, the willingness to die for a comrade more than dying for a cause, the struggle to stay dry, stay fed, stay low — these are eternal verities in war."

The 66-year-old Atkinson completed his World War II books in 2013, and considered writing about the conflict in the Pacific before deciding that it didn't have "the same hold" on his interest. He instead looked to the American Revolution, a favorite subject since childhood, as a way of exploring "who we are, where we came from and what our ancestors were willing to die for."

"The British are Coming" is more than 500 pages (not including a 42-page bibliography) and covers the years 1775-77, from the first shots at Lexington and Concord to the aftermath of the battles of Trenton and Princeton, when George Washington's battered army managed to push back against the British and revive the colonists' hopes. Atkinson's narrative blends general reflections on war with the most specific touches, whether the shadows cast by the elm trees on Boston Common or the amount of rum (2 ounces) that troops in Princeton, New Jersey, were encouraged to drink to maintain their courage.

"Those details are the mother's milk of narrative writing," Atkinson says. "One of the things I found was claims made by widows of men killed in Lexington and Concord. You have widows putting in for trousers or his pipe or his musket. These are small fragments of a world destroyed, of an individual family. And it tells you something about the way society worked."

Atkinson contrasts the war's opposing Georges: King George III and George Washington. The King George documents upended for him the image of George as a whiny "nitwit," as immortalized in the musical "Hamilton," or the raving monarch in Alan Bennett's play "The Madness of King George." He was "not easy to like," Atkinson acknowledges, but the author found him a "formidable, interesting character," one as likely to write down a recipe for cough syrup as make a decision on how many warships to commit to the American conflict.

Washington, meanwhile, transforms during the first volume from an "aggressive and even reckless" leader with an "aloof" demeanor to a more sophisticated strategist with a growing understanding of his soldiers.

"In 1775, he's pretty unpleasant about the rabble he's commanding," Atkinson says. "He's very snide about the army he's taken over, but over the first two years this mystical bond develops between the commander and commanded. He recognizes that he must learn to lead them. He writes very eloquently about a people not used to being commanded. He realizes that they cannot be driven, they must be led."