In September 1941, General Douglas MacArthur requested Casey's services as his chief engineer. Casey arrived in Manila in October, shortly before the outbreak of war between the United States and Japan. He acquired construction equipment from the National Power Corporation that was being used on the Caliraya project. Casey supervised demolitions as MacArthur's troops retreated to Bataan, for which he was awarded the Distinguished Service Cross. Unlike the rest of MacArthur's headquarters, Casey, who was promoted to colonel on 19 December 1941 and brigadier general on 25 January 1942, did not relocate to Corregidor but remained on Bataan with a small staff of five officers. However, he joined MacArthur and sixteen other members of his staff in their escape from Corregidor by PT boat in March 1942. For his service in the 1942 campaign in the Philippines, he was awarded the Army Distinguished Service Medal.