Alistair Horne, historian and biographer, in 2012. (David Levenson/Getty Images)

Alistair Horne, a onetime British intelligence officer whose graceful, fast-paced books on France and military history were bestsellers and enjoyed renewed influence among political leaders and counterinsurgency experts during the Iraq War, died May 25 at his home in Turville, England. He was 91.

His death was first reported by the Daily Telegraph, a British paper for which Mr. Horne once worked as a foreign correspondent. The cause was not disclosed.

During a six-decade writing career, Mr. Horne published more than 20 books, including biographies, memoirs and several studies of France, from the age of Napoleon to modern times.

Mr. Horne’s breakthrough came in 1962 with his fourth book, “The Price of Glory: Verdun 1916,” about a 10-month battle in World War I with 700,000 casualties.

“No historian of our times,” author Leon Wolff wrote in a New York Times review, “has so poignantly recaptured the malignancy of war on the Western Front.”

“The Price of Glory” was awarded Britain’s Hawthornden Prize as the best book of the year, fiction or nonfiction. Mr. Horne’s later books about France’s military rivalry with Germany, “The Fall of Paris: The Siege and the Commune, 1870-71” (1965) and “To Lose a Battle: France 1940” (1969), also won stellar reviews and legions of readers.

His 1977 account of the Algerian War, “A Savage War of Peace: Algeria 1954-1962,” recounts how an insurgency movement defeated the French military and led to independence for the North African country.

The Algerian War, Mr. Horne said in 2007, was “a prototype of the modern war of national liberation.” Guerrilla leaders from South Africa to the Middle East read the book attentively, as did military leaders and diplomats in the West.

A quarter-century after it was published, “A Savage War of Peace” became an underground bestseller among counterinsurgency officers searching for greater understanding of the perils they would likely face in the U.S. incursion into Iraq in 2003. Used copies were selling for hundreds of dollars before the book was republished in 2006.

In an introduction to the new edition, Mr. Horne drew explicit connections between Algeria and Iraq. He noted that France alienated its Muslim foes in Algeria — and many Western countries, as well — through the use of torture, writing, “Torture should never, never, never be resorted to by any Western society.”

In 2006, former secretary of state Henry Kissinger — the subject of another of Mr. Horne’s books — sent a copy of “A Savage War of Peace” to the White House. Mr. Horne was later summoned to the Oval Office for a private meeting with President George W. Bush.

“He questioned me closely about the parallels between Iraq and Algeria,’’ Mr. Horne later wrote in the Daily Telegraph. “It was clear that he had read attentively what I had written.”

Bush spoke of his determination to stay the course in Iraq.

“I recalled that the Algerian War lasted eight years,” Mr. Horne wrote, “and, at the end, France’s de Gaulle had lost his shirt, everything.”

The former Israeli prime minister Ariel Sharon, who said Mr. Horne’s 1969 book “To Lose a Battle: France 1940,” helped Israel prevail in the 1973 October War against Egypt, described “A Savage War of Peace” as his favorite bedtime reading.

Alistair Allan Horne was born Nov. 9, 1925, in London. His father was a businessman. His mother died in a car accident in Belgium when her son was 4.

After attending a series of grim boarding schools in England, Mr. Horne came to the United States in 1940 to escape the German bombing blitz of his homeland. He was taken in by an American family and attended the private Millbrook School in Millbrook, N.Y. In a 1994 memoir, “A Bundle From Britain,” he called his experience there “the only childhood I had ever had.”

One of his closest friends at Millbrook was William F. Buckley Jr., who went on to be a conservative commentator, television host and founder of the magazine National Review.

Mr. Horne returned to Britain in 1943 and became an officer in the British army’s elite Coldstream Guards and held intelligence posts in Cairo and the British Mandate of Palestine.

He graduated from the University of Cambridge in 1949 and, within a few years, was a correspondent in Germany for the Daily Telegraph. On the side, he worked for the British intelligence service and transported documents in a suitcase with a false bottom.

Mr. Horne lost his job at the Telegraph after he refused to check on a train schedule for the wife of the paper’s publisher, saying she could look it up herself. He then wrote books about Germany, the United States and Canada before publishing “The Price of Glory.”

His marriage to Renira Hawkins ended in divorce. Survivors include his wife since 1987, ­Sheelin Ryan Eccles; three daughters from his first marriage; and five grandchildren.

Mr. Horne also wrote books about Chile in the early 1970s, British World War II general Bernard Montgomery, Kissinger’s diplomacy, Napoleon and, repeatedly, “La Belle France” — the title of a 2005 history of the country.

The publishing executive who suggested that Mr. Horne write about the French in Algeria was Harold Macmillan, who had served as Britain’s prime minister from 1957 to 1963.

Mr. Horne later wrote a two-volume biography of Macmillan under the agreement that it not appear until after Macmillan’s death, which came in 1986. Mr. Horne spent hundreds of hours interviewing Macmillan, eliciting intimate personal stories and a revealing look at the highest levels of the British government.

Asked how he drew so much information out of the taciturn prime minister, Mr. Horne said, “The short answer is: with quite a lot of whisky.”