The Defense Ministry commissioned a study into the possible conversion of the Maritime Self-Defense Force's Izumo helicopter carrier into a full-fledged aircraft carrier in case Japan was required to provide rear-line support for a U.S.-led war.

The ministry in April 2017 asked Japan Marine United Corp., a Tokyo-based company that built the vessel, to look into ways to improve the capabilities of the Izumo.

Japan Marine United submitted its report to the Defense Ministry in March and the ministry released details, with some bits blacked out, on April 27.

The report states that the Defense Ministry's precondition for the study was to look into how the Izumo could be used to provide rear-line support to the U.S. military.

The company was asked to provide estimates for the cost and construction schedule if changes were made to allow U.S. F-35B stealth fighter jets to land vertically on the deck and to use elevators to transport aircraft to their hangars.

No mention was made in the study for having the SDF use the improved Izumo.

Some portions of the released report were redacted, including details on what changes would be needed to transform the Izumo into an aircraft carrier, as well as the costs to make the changes and the duration of the project.

The Defense Ministry had contended that it never considered converting the Izumo, and officials maintained that position even with the release of the study report.

One official said the study was conducted because, with the deployment of F-35B fighter jets to U.S. Marine Corps Air Station Iwakuni in Yamaguchi Prefecture, the need might arise to use the Izumo as a carrier during joint Japan-U.S. military training or when U.S. aircraft experienced mechanical problems.

However, one government source did not rule out the possibility of the Izumo eventually being converted into an aircraft carrier.

This viewpoint is in line with Prime Minister Shinzo Abe's policy that Japanese forces could be utilized to provide support to the U.S. military during situations where Japan's survival is threatened or situations that would harm this country's interests.

(This article was written by Takateru Doi, a senior staff writer, and Hirotaka Kojo.)