From 1924 all new cargo ships for NYK were motor ships NYK introduced its first passenger motor ships in 1929 but continued to buy a mixture of steam and motor passenger ships until 1939.
In World War II the NYK Line provided military transport and hospital ships for the Imperial Japanese Army and Navy. Many vessels were sunk by the Allied navies, and installations and ports were attacked from the air. Only 37 NYK ships survived the war. The company lost 185 ships in support of military operations in the Pacific.[9] Before the war NYK had 36 passenger ships by the time of Japan's surrender only one, the motor ship Hikawa Maru, survived.
NYK's surviving vessels and equipment were confiscated by the Allied authorities as reparations, or taken by recently liberated Asian states in 1945-46. SCAJAP requisitioned Hikawa Maru as a transport ship to repatriate Japanese soldiers and civilians from territories that had been liberated from Japanese occupation.[10]