Mitsubishi Heavy will restart an idle Tamano slipway to build Japan's largest navy supply ship

Mitsubishi Heavy Industries plans to bring a dormant shipbuilding line in Tamano, in Okayama prefecture in western Japan, back into use in fiscal 2027 to build a new replenishment ship for Japan's Defence Ministry, Nikkei Asia reported on Sunday, Oct. 18. Kyodo News, citing a source close to the matter, reported the same plan on Monday, Oct. 19, and said the aim is to expand construction capacity as higher defence spending and a push to export naval vessels drive up demand for ships.

The line sits at the main plant of Mitsubishi Heavy Industries Maritime Systems, a group company based in Tamano. According to Nikkei Asia, the plant has two slipways for building and repairing ships on land and two excavated dry docks. The slipway due to restart is about 250 metres long and has been idle since a small vessel was built there in 2024. The replenishment ship would be the first large vessel built at the site since Mitsubishi Heavy took it over. The yard currently builds destroyers, Japan Coast Guard patrol vessels and other specialised ships.

The plant previously belonged to the former Mitsui Shipbuilding and Engineering, now Mitsui E&S, which decided to leave its struggling naval shipbuilding business. Mitsubishi Heavy took over the operation in 2021, which kept the plant working, both reports said.

The new ship is meant to carry fuel and supplies to the fleet. Nikkei Asia said it is expected to become the largest replenishment ship in the Japan Maritime Self-Defense Force, surpassing the Towada and Mashu classes that now fill that role. Kyodo said the restart will come with more staff for shipbuilding at the site. Nikkei Asia reported that the company plans to hold down investment by reusing existing cranes and other equipment, and to work with partner companies to raise the number of people involved in shipbuilding there by about 50 percent.

Mitsubishi Heavy already has several naval projects under way. It is building vessels fitted with the Aegis combat system at its Nagasaki shipyard. It also holds a contract with the Australian government for three upgraded Mogami-class frigates of about 4,800 tons for Australia's General Purpose Frigate programme. Canberra chose the design as its preferred option in August 2025, and the company said in April 2026 that construction would start at Nagasaki, with the first ship to be handed over by December 2029. Nikkei Asia described the Australian order as Japan's first postwar export of warships.

Policy is driving the demand. Japan's defence spending has risen sharply since fiscal 2023, and Tokyo brought forward its goal of spending 2 percent of gross domestic product on defence to fiscal 2025, two years earlier than first planned. In April the government lifted restrictions on exports of defence equipment with offensive capabilities, and Nikkei Asia said other possible warship export deals are under consideration.

Capacity is the constraint. Japanese shipbuilders cut back their naval construction capacity over many years while the defence budget stayed flat. Nikkei Asia reported that reopening idle facilities will help, but that finding skilled workers for tasks such as design and welding remains a challenge. The revival is also reaching commercial yards: Hakodate Dock, a Namura Shipbuilding subsidiary on Hokkaido, has decided to reopen a commercial shipbuilding dock that has been idle since 1993.

Neither report gave a delivery date or a cost for the new replenishment ship, or said how many of the class the Defence Ministry intends to order.