In this file photo, USNS Mercy (T-AH 19) transits the Pacific Ocean in late May. (U.S. Navy/MCC Christopher E. Tucker)

SAN DIEGO - The hospital ship USNS Mercy (T-AH 19) is scheduled to return Sept. 27, along with embarked Helicopter Sea Combat Squadron (HSC) 21 Sept. 26, from a four-month deployment in support of Pacific Partnership 2015.

The tenth iteration of the U.S. Pacific Fleet's annual humanitarian assistance/disaster relief preparedness mission began in late May and took place in the Southeast Asia and Oceania regions.

Born out of the devastation wrought by the 2004 tsunami that swept through parts of Southeast Asia, Pacific Partnership began as a military-led humanitarian response to one of the world's most catastrophic natural disasters. Building on that success and goodwill, the hospital ship USNS Mercy returned to the region in 2006 for the inaugural Pacific Partnership mission. The mission staff expanded to include partner nation militaries and non-governmental organizations working to increase the disaster relief capabilities in the region. Since then, Pacific Partnership has grown in scope and size.

Mercy visited Fiji, Papua New Guinea, the Philippines, and Vietnam. Mercy provided healthcare and surgical procedures, community health engagements, engineering projects, subject matter expert exchanges and community relations events in coordination with host nations, NGOs and regional partners that included Australia, New Zealand, Japan, Republic of Korea, Malaysia, Canada, Timor Leste, and Fiji.

The PP15 medical team performed surgical and healthcare procedures both on and off the ship, performing nearly 700 surgeries aboard the Mercy; the PP15 dental team provided dental care to more than 3,800 patients; and PP15 engineers worked side-by-side to complete a total of 10 renovation and new construction projects including school buildings, community centers, medical facilities and a disadvantaged youth center, which also double as disaster shelters.

Also returning home today on the east coast is USNS Comfort, USNS Mercy's sister ship, who just completed a nearly six-month deployment supporting Continuing Promise in Central America and the Caribbean. Continuing Promise 2015 mission were conducted in Honduras, Haiti, Belize, Guatemala, Jamaica, Nicaragua, Panama, El Salvador, Colombia, Dominica and the Dominican Republic.

See photos from Pacific Partnership 2015 in the U.S. Pacific Fleet Flickr stream.