Regeneration Trilogy
Following the publication of Liza's England, Barker felt she "had got myself into a box where I was strongly typecast as a northern, regional, working class, feminist—label, label, label—novelist. It's not a matter so much of objecting to the labels, but you do get to a point where people are reading the labels instead of the book. And I felt I'd got to that point", she said in 1992. She said she was tired of reviewers asking "'but uh, can she do men?' – as though that were some kind of Everest".
Therefore, she turned her attention to the First World War, which she had always wanted to write about due to her step-grandfather's wartime experiences. Wounded by a bayonet and left with a scar, he would not speak about the war. She was inspired to write what is now known as the Regeneration Trilogy—Regeneration (1991), The Eye in the Door (1993), and The Ghost Road (1995)—a set of novels that explore the history of the First World War by focusing on the aftermath of trauma. The books are an unusual blend of history, with real life characters, and fiction, and Barker draws extensively on the writings of First World War poets and W. H. R. Rivers, an army doctor who worked with traumatised soldiers. The main characters are based on historical figures, such as Robert Graves, Alice and Hettie Roper (pseudonyms for Alice Wheeldon and her daughter Hettie Wheeldon) with the exception of Billy Prior, whom Barker invented to parallel and contrast with British soldier-poets Wilfred Owen and Siegfried Sassoon. As the central fictional character, Billy Prior is in all three books.
“I think the whole British psyche is suffering from the contradiction you see in Sassoon and Wilfred Owen, where the war is both terrible and never to be repeated and at the same time experiences derived from it are given enormous value," Barker told The Guardian. "No one watches war films in quite the way the British do."
Barker told freelance journalist Wera Reusch "I think there is a lot to be said for writing about history, because you can sometimes deal with contemporary dilemmas in a way people are more open to because it is presented in this unfamiliar guise, they don't automatically know what they think about it, whereas if you are writing about a contemporary issue on the nose, sometimes all you do is activate people's prejudices. I think the historical novel can be a backdoor into the present which is very valuable."
The Regeneration Trilogy was extremely well received by critics, with Peter Kemp of the Sunday Times describing it as "brilliant, intense and subtle", and Publishers Weekly saying it was "a triumph of an imagination at once poetic and practical." The trilogy is described by The New York Times as "a fierce meditation on the horrors of war and its psychological aftermath." Novelist Jonathan Coe describes it as "one of the few real masterpieces of late 20th century British fiction." British author and critic, Rosemary Dinnage reviewing in The New York Review of Books declared that it has "earned her a well-deserved place in literature" resulting in its re-issue for the centenary of the First World War. In 1995 the final book in the trilogy, The Ghost Road, won the Booker–McConnell Prize.