Former US marine Phil Klay has won the £25,000 Warwick prize for writing with his “scaldingly affecting” collection of short stories detailing the Iraq war.

Redeployment beat titles including Karl Ove Knausgaard’s A Man in Love, Karen Joy Fowler’s We Are All Completely Beside Ourselves and Marilynne Robinson’s Lila to the award, given every two years, which is open to any genre or form of writing, and which this year took the theme of “instinct”.

Featuring stories from the perspectives of soldiers on the frontline, military wives back in the US, and veterans dealing with the after-effects of war, Redeployment is “characterised by a harrowing authenticity and a nuanced insight that can only be acquired through frontline experience”, said Warwick University. Klay joined the marines in the run-up to the Iraq war in 2003, serving as a public affairs officer in Anbar province and took an MFA at Hunter College after his return.

Author AL Kennedy, who chaired the judging panel, called Redeployment a “scaldingly affecting book” which has “translated personal knowledge into living fiction” as it addresses one of the “defining conflicts of our age”.

“We were all held by it,” said Kennedy, who is an associate professor at Warwick. “There is remarkable control, delicacy and subtlety in the spare style of prose here and a real grip of various psychologies and voices across the collection.”

Redeployment won praise from Barack Obama, with the US president calling it “a quick but powerful and, for me, painful set of stories about the experience of ordinary soldiers in Iraq”. The Guardian’s review described the book as “a series of increasingly sophisticated portraits of men pulled apart by competing and contradictory feelings”, which is “the real thing – a vivid and vital battery of war stories that does not rely solely on its subject matter for impact (although, make no mistake, the subject certainly has impact)”.

The collection won the National Book award for fiction last November, judges at the time saying that “if all wars ultimately find their own Homer, this brutal, piercing, sometimes darkly funny collection stakes Klay’s claim for consideration as the quintessential storyteller of America’s Iraq conflict”.

Previous winners of the Warwick award include Naomi Klein, for The Shock Doctrine, and Alice Oswald for Memorial. Kennedy was joined on this year’s judging panel by the writers Robert Macfarlane and Gavin Francis, the actor and director Fiona Shaw, and the Lonely Planet founder Tony Wheeler.