the . The first one of these ships was laid down in 2012 and was launched on 6 August 2013. The submarine fleet of the JMSDF consists of some of the most technologically advanced diesel-electric submarines in the world. This is due to careful defense planning in which the submarines are routinely retired from service ahead of schedule and replaced by more advanced models. In 2010 it was announced that the Japanese submarine fleet would be increased in size for the first time in 36 years. After a meeting between the Japanese Foreign Minister and U.S. Ambassador to Japan on 4 March 2014, the Japanese Defense Ministry and U.S. Department of Defense announced they would hold studies for the joint development of the littoral vessel under the bilateral Mutual Defense Assistance Agreement. The vessel is planned to be a high-speed trimaran designed for operations in shallow coastal waters capable of carrying helicopters, possibly a lighter variant of the American littoral combat ship. The study is in response to the growth of the Chinese People's Liberation Army Navy and budgetary issues with the U.S. military that may affect their ability to operate in the Pacific. The J-LCS would be used to intervene during Chinese ship incursions near the Senkaku Islands and other contested areas in the East China Sea, and possibly counter similar Chinese vessels like the Type 056 corvette and Type 022 missile boat. A J-LCS with an enlarged hull could operate the SH-60K anti-submarine helicopter or the MCH-101 airborne mine countermeasures (AMCM) helicopter. On May 1, 2017, was dispatched to protect a U.S. Navy supply vessel in the Pacific. This was the first time the JMSDF has been used to defend allied vessels since the 2016 amendment to the Japanese Constitution. Japan christened the long, JS Ōryū submarine on October 4, 2018. It is Japan's first submarine powered by lithium-ion batteries and was developed by Mitsubishi Heavy Industries. The Japan Maritime Self-Defense Force will utilize it by March 2020. Japan and the United States conducted the biggest military exercise around Japan thus far in the biennial Keen Sword from 29 October to 2 November 2018. It included a total of 57,000 sailors, marines and airmen. 47,000 service members were from the JSDF and 10,000 from the U.S. Armed Forces. A naval supply ship and a frigate of the Royal Canadian Navy also participated. There were simulations of air combat,