Recognized by his commanders and peers as an innovative artilleryman, Kerwin developed a system of massing fires that contributed immeasurably to the success of the Allied landings at Anzio Beachhead. After World War II, he attended the Army War College and the National War College, and served in various assignments, including Plans and Operations Officer at the Los Alamos Scientific Laboratory; Commander of the 56th Artillery Group, XVIII Airborne Corps; and Deputy Director in the Army's Office of the Chief of Research and Development.