In March 1918 he was promoted to Major and given command of 74 "Tiger" squadron equipped with the SE5A, which he took to France on 30 March. Under Caldwell's guidance the squadron claimed a creditable 140 aircraft destroyed and 85 'out of control' in the remaining eight months of the war, for a modest 15 pilots killed or prisoner. Caldwell fought his last combat on 30 October 1918, claiming his 9th Fokker D.VII. Altogether he is credited with 11 aircraft destroyed, 2 shared destroyed, 1 shared captured, and 10 and 1 shared 'out of control'. Virtually all of his victims were single-seat scouts. He was awarded the Distinguished Flying Cross in December 1918, the citation being "A fine fighting airman of courage and determination. On 4th September, when on offensive patrol, he, in company with another machine, attacked four Fokker biplanes; one of these was driven down by this officer. He has accounted for five enemy machines."