Kersh was drafted into the army during the Second World War, served in the Coldstream Guards and ended up writing for the Army Film Unit. Despite apparently deserting, Kersh ended up in France during the liberation, where he discovered that many of his French relatives had ended up in Hitler's extermination camps. After the war, Kersh continued to enjoy commercial success, mainly because of his short stories, in genres such as horror, science fiction, fantasy and the detective story. From about the mid-1950s onwards, he started to suffer from poor health and financial hardship (specifically relating to his failure to pay income tax). However, Kersh continued to publish novels and stories, some of which were commercially and critically successful. In 1958, his short story "The Secret of the Bottle", originally published in "The Saturday Evening Post", received an Edgar Award from the Mystery Writers of America. The following year he became a U.S citizen.