Mr. Keegan was a writer of exceptional grace whose more than 20 books spanned the history of warfare from Alexander the Great to the 21st-century U.S. incursion in Iraq. In the New York Times Book Review in 2009, Civil War historian James M. McPherson called him “our generation’s foremost military historian.”
The work that established Mr. Keegan’s reputation was “The Face of Battle” (1976), which examined warfare from the perspective of soldiers taking part in three historical European battles: Agincourt in 1415; Waterloo in 1815; and the 1916 Battle of the Somme, during World War I.
In the book, Mr. Keegan made it clear that his approach was a departure from conventional historical writing, “with its reduction of soldiers to pawns, its discontinuous rhythm, its conventional imagery, its selective incident and its high focus on leadership.”
Instead, he described the conditions at the battlefront with a visceral realism, depicting the deafening noise, blinding smoke, slippery gore, confusion, stench and fear that accompanied soldiers in war.
All battles, regardless of their era, Mr. Keegan argued, were fought by soldiers “struggling to reconcile their instinct for self-preservation, their sense of honor and the achievement of some aim over which other men are ready to kill them.”
He was particularly eloquent in writing about the brutality of the first day of the Battle of the Somme, on July 1, 1916: “In all, the British had lost about 60,000, of whom 21,000 had been killed, most in the first hour of the attack, perhaps the first minutes.”
The conditions of the battle were so abhorrent, he wrote, with “long docile lines of young men, shoddily uniformed, heavily burdened, numbered about their necks, plodding forward across a featureless landscape to their own extermination,” that they could be compared only to the Nazi concentration camps of World War II.
“Accounts of the Somme,” Mr. Keegan wrote, “produce in readers and audiences much the same range of emotions as do descriptions of the running of Auschwitz — guilty fascination, incredulity, horror, disgust, pity and anger.”
Historian Neal Ascherson, writing in the New York Review of Books, said that “The Face of Battle” had “no counterpart in the literature of war.”
British historian J.H. Plumb, in the New York Times Book Review, pronounced it “a brilliant achievement” that was “as much about the nature of man as of battle.”
Mr. Keegan went on to write other influential books exploring the nuances of warfare, including “Six Armies in Normandy” (1982), about the D-Day Invasion of France during World War II, and “The Mask of Command” (1987), which concluded that the best military commanders projected strength through a strong sense of theatricality that inspired their soldiers to follow them into battle.