Japan opens door to warship exports as Mitsubishi Heavy restarts dormant shipyard line

As Japan pushes ahead with deregulation of defense equipment exports and demand for warships grows, Mitsubishi Heavy Industries is reactivating a dormant shipbuilding line to expand its construction capacity.

The Nikkei reported Monday that Mitsubishi Heavy Industries has decided to restart one of the shipbuilding lines at its shipyard in Tamano, Okayama Prefecture, next year. The line features a slipway approximately 250 meters long that has sat unused since the company built a single small vessel there in 2024.

Mitsubishi Heavy Industries plans to use the line to build a new replenishment ship for Japan's Defense Ministry. The vessel would be the largest replenishment ship ever built for the Maritime Self-Defense Force, surpassing the existing Towada-class and Mashu-class ships. It will also be the first large vessel built at the shipyard since Mitsubishi Heavy Industries acquired it from Mitsui E&S Holdings.

The decision to restart the dormant facility follows Japan's revision of its Three Principles on Transfer of Defense Equipment in April, which lifted a longstanding ban on the export of lethal weapons and opened the door to warship exports. Japanese shipyards had been scaling back their warship-building capacity for years, as the country had not increased its defense budget and demand for new vessel construction remained low.

The cabinet of Prime Minister Sanae Takaichi is pursuing a defense budget increase to between 3 and 3.5 percent of GDP and has authorized the export of lethal weapons, generating new demand for warships. Mitsubishi Heavy Industries has also won a contract to build Australia's next-generation frigates — what the Nikkei described as Japan's first warship export since World War II.

Beyond restarting the Tamano shipbuilding line, Mitsubishi Heavy Industries is also building an Aegis-equipped vessel at its Nagasaki shipyard.