"Arthur Foss" was placed in service by the U.S. Navy in early 1942, renamed "Dohasan" and designated YT-335 (harbor tug) and later YTM-335 (district harbor tug, medium). The tug continued to tow supply barges between bases in the Hawaiian archipelago and even ventured as far as French Frigate Shoals, northwest of Oahu. "Dohasan" towed a large grab dredge to the Shoals on 8 August 1942 for construction of an emergency landing strip there, then remained as a tender to the dredge as it removed material from the lagoon and deposited it ashore to build up and form a runway. The tug returned to Hawaii after three months of this work, but afterward apparently spent a lot of time idle as navy crews were unfamiliar with operation of the main engine. After the war ended in September 1945, "Dohasan" continued in naval service until being stricken from the Navy List on 7 February 1945 and lay up at Honolulu through 1946. The tug was finally returned to Foss Launch & Tug Company ownership in fall 1947, and renamed "Arthur Foss". To return the worn-out tug to the West Coast, CPNAB secured it in a floating drydock and had it towed to Los Angeles. During the stormy voyage, rough seas knocked "Arthur Foss" off its keel blocks, heavily damaging the hull. Upon arrival back in Tacoma, Foss began a comprehensive rehabilitation of the tug which occupied it until August 1948.