JR Potts, AUS 173d AB and Dan Alex (Updated: 6/29/2016):
The need for the Izumo is due to the arms race emerging between the nations bordering the Sea of Japan as well as the East and South China Seas. The area is dotted by hundreds of islands and reefs which also places them in regular dispute - both territorial and for the natural resources they hold. This geopolitical location provides an abundance of fish, natural gas and oil reserves making the South China Sea particularly attractive to industrialized (and emerging) nations like Japan, China, Taiwan, the Philippines, North and South Korea, Vietnam, Thailand and Cambodia. Add to this the fact that one-third of all global shipping transits through these disputed waters and interest in the region's stability expands beyond Southeast Asia and the Pacific. Advanced Chinese destroyers, carrying cruise missiles, have been spotted near the gas fields of the East China Sea during 2013 - such measures not going unnoticed and serving to heighten tensions for all parties. Indeed the American focus is turning from the Middle East to the Pacific.
The 22DDH-class helicopter destroyers were partly designed to patrol the disputed sea lanes and protect Japanese merchant shipping with the intent that they will eventually replace the aging Shirane (DDH-143) and her sister ship Kurama (DDH-144) as well as four other destroyers scheduled to begin decommissioning in fiscal 2014 with no other replacement ships being constructed. The JMSDF feels that two 22DDH-class warships can fill the loss of these six destroyers without the need to add more ships, thus reducing military naval spending.
Izumo was laid down on January 27th, 2012 and launched from the Yokohama dockworks on August 6th, 2013. The unveiling date also served as remembrance for the atomic bomb strike on the city of Hiroshima in 1945. The dimensions of the Izumo allow the vessel to respond adequately to emergency assistance missions in home waters and through international peacekeeping requests. The helicopter destroyer has a capability to transport up to 4,000 personnel or some fifty military trucks. Additionally, the class holds the capacity to provide fuel to other Japanese warships in the fleet as required. This underway replenishment would eliminate the need for ships to drop anchor to refuel, saving steaming time. As such, the decision was made not to construct dedicated destroyer or supply ship types - instead to design, develop and construct "multi-mission" platforms consistent with other world powers, ships to serve multiple purposes on the high seas. So the "bigger the better" approach has allowed the Izumo to expand her base mission capabilities considerably. When compared to previous helicopter destroyer models, Izumo is 165 feet longer and 22 feet wider with a hanger deck 150 feet longer and 20 feet wider - all told close to a 50% increase in internal volume and deck space.