Japanese Merchant Shipping Routes 1941–45

Japanese shipping routes spanned far and wide, taking in Indonesia, the Philippines, the Pacific Island groups, New Guinea and the Dutch East Indies. The ships were the lifelines for the far-flung Japanese outposts of war, providing ammunition, troops, fuel and food to garrisons across the Pacific. Equally important was the return of these ships, supplying the Japanese home islands (which had few natural resources) with coal, iron, oil and food. American submarines targeted the Japanese merchant ships, aiming to disrupt this two-way supply process and starve the war effort both at home and across the Japanese war empire. As the war progressed, Allied submarine warfare significantly improved, yet the Japanese failed to adapt. As a result they suffered a huge shipping defeat; it is estimated they lost over 3,000 battle and merchant ships.