Following service in the Middle East, Evans joined RAF Fighter Command where he was a signals officer at the outbreak of the Second World War. In 1941, he was given command of the Fighter Interception Unit at Ford and was responsible for introducing successful new tactics. He personally shot down two enemy fighters and was awarded the Distinguished Flying Cross in 1942. At the age of thirty, he was promoted to group captain and went to Headquarters No. 11 (Fighter) Group in charge of night operations. In 1943, he was posted to the Mediterranean where he undertook the air side of signals planning for the Sicily invasion. Later he performed similar duties in the Allied Expeditionary Air Force for the Normandy landings.