Guam is the westernmost U.S. territory long valued as strategically significant to U.S. forward deployments in the Western Pacific. Historically, the United States acquired Guam from Spain in 1898 after the Spanish-American War. In the Pacific Ocean, Hawaii is about 2,400 miles west of California, and Guam is about 3,800 miles further west of Hawaii. Guam has two important U.S. military bases: Apra Naval Base and Andersen Air Force Base. The island, three times the size of Washington, DC, is home to about 160,000 people. There are about 6,000 military personnel. As the Defense Department faced increased tension on the Korean peninsula, the Pacific Command (PACOM) based in Honolulu began in 2000 to build up air and naval forces on Guam to boost U.S. deterrence and power projection in Asia. Concerns include crisis response, counterterrorism, and contingencies in the Pacific. The defense buildup on Guam has been moderate. Guam is critical to enhancing the forward presence, strengthening alliances, and shaping China's rise. Visiting Guam in May 2008, Defense Secretary Robert Gates said that Guam's buildup will be "one of the largest movements of military assets in decades" and will help to "maintain a robust military presence in a critical part of the world." Under President Obama, Secretary Gates issued the Quadrennial Defense Review (QDR) in February 2010, in which the United States noted the importance of implementing the U.S.-Japan Realignment Roadmap of 2006 that will ensure the deployment of U.S. forces in Japan and transform Guam into a regional security hub. The QDR also announced the development of a new joint Air-Sea Battle Concept, to integrate the air, sea, land, space, and cyberspace forces of the Air Force and Navy to counter challenges to U.S. freedom of action, defeat adversaries with sophisticated anti-access and area-denial (A2/AD) capabilities, and improve power projection operations. As part of the Obama Administration's effort to re-engage throughout the Asian-Pacific region and reassure allies and partners facing a rising China that views the United States as an "outside" power, Gates participated at an annual Asian-Pacific defense ministers' meeting in June 2010 in Singapore at which he declared that the United States is a Pacific nation and will remain a "power in the Pacific." He highlighted the South China Sea as an area of growing concern. He also stated that the defense buildup on Guam is part of a shift in the U.S. defense posture in Asia, a shift to be more geographically distributed, operationally resilient, and politically sustainable. Deputy Defense Secretary William Lynn III visited Guam in July and stressed Guam's value, saying "from bases here, our forces can ensure the security of our allies, quickly respond to disaster and humanitarian needs, safeguard the sea lanes that are so vital to the world economy, and address any military provocation that may occur." The Chairman of the Joint Chiefs of Staff issued strategic guidance for 2011 that placed priority on U.S. security interests in the Middle East, Afghanistan, and Pakistan. Still, he declared a sharper focus on the Asian-Pacific region in balancing risks from an aggressive North Korea and a more assertive China and in defending freedom of navigation. With the U.S. military's drawdown from Afghanistan and Iraq, the U.S. defense strategy of January 2012 declared a "rebalancing" toward a strengthened presence in the Pacific. In May 2014, Defense Secretary Chuck Hagel said that the Deputy Secretary of Defense will oversee the enhancement of the U.S. force posture in Guam, Japan, and South Korea. Guam's strategic significance has risen steadily. In 2000, the Air Force reportedly sought to base elements of an Air Expeditionary Force in Guam and sent B-2 stealth bombers to Guam to expand the range of U.S. options for contingencies involving North Korea. As PACOM's Commander, Admiral Dennis Blair acquired approval to forward deploy air-launched cruise missiles on Guam for the first time in August 2000. The Air Force moved precision munitions to be stockpiled on Guam, including Joint Direct Attack Munitions and Joint Standoff Weapons. In February 1997, Guam's Delegate Robert Underwood noted in the House that an aircraft carrier (USS Independence , homeported in Japan) visited Guam for the first time in more than 30 years. In 2001, the Navy announced that it would station up to three nuclear-power attack submarines (SSNs) at Guam, shortening the travel time compared to travel from homeports in Hawaii or California to the western Pacific and shortening deployments for sailors. The first submarine to be based at Guam arrived in 2002. In 2007, the USS Buffalo joined USS Houston and USS City of Corpus Christi as the three SSNs based at Guam. (Since then, different SSNs have replaced those first SSNs with their homeports in Guam.) The Quadrennial Defense Review (QDR) of 2006 called for an adjustment in U.S. force posture, with a greater presence in the Pacific than that in the Atlantic (including at least six aircraft carriers and 60% of submarines in the Pacific). In 2007, the Navy decided not to homeport the aircraft carrier USS Carl Vinson at Guam. In 2008, the Navy proposed a transient berth in Apra Harbor to support a carrier for up to three times a year, each visit for up to three weeks, but the Navy later deferred the idea indefinitely. The QDR of 2010 called for maintaining a force structure of 10-11 aircraft carriers. In mid-2010, three Ohio-class guided-missile submarines (SSGNs), USS Michigan , USS Ohio , and USS Florida , showed their presence in the Pacific and used Guam to support their operations. In June 2012, five Los Angeles-class SSNs and one Ohio-class SSGN simultaneously converged at Guam, in part for repairs and maintenance. In June 2012, Defense Secretary Leon Panetta provided some details for the strategic "rebalance" to the Asia-Pacific, saying that, by 2020, 60% of the Navy's fleets would be in the Pacific, including 6 of 11 aircraft carriers. On April 8, 2013, Deputy Secretary of Defense Ashton Carter announced that the Navy will deploy a fourth SSN to Guam by 2015. The Navy announced in February 2014 that the USS Topeka will be that SSN. Guam's three SSNs form part of the force of 56% of total SSNs that are deployed to the Pacific, as of August 2014. In 2002, the Commander of Pacific Air Forces publicly detailed his request for basing aircraft in Guam. In addition to munitions stockpiles and jet fuel, he reportedly requested F-22 stealth fighters, 767 tankers, C-17 transports, bombers, and Global Hawk reconnaissance drones. In March 2003, after a new Air Expeditionary Wing was activated at Guam's Andersen Air Force Base, B-1 and B-52 bombers deployed temporarily on a rotational basis from air bases in Texas and Louisiana as U.S. forces prepared for war against Iraq. Beyond rotation of aircraft, the Air Force began continuous deployment of aircraft into Guam. As part of this buildup, the first B-52 bombers (stationed out of Minot Air Force Base in North Dakota) to deploy to Andersen arrived in February 2004. B-52 bombers can each carry 20 AGM-86C/D conventional air-launched cruise missiles (CALCMs), and these long-range weapons have been fielded at Andersen. In April 2005, the Commander of Pacific Air Forces said that B-2 stealth bombers started to fly out of Andersen. In April 2005, F-15 fighters temporarily deployed to Andersen from Idaho. An Air Force official said in 2006 that the Air Force planned to station KC-135 tankers on Guam. In May 2007, the Air Force announced the deployment of 18 F-16 fighters to Guam for four months. In the summer of 2008, several F-22 fighters, based in Alaska since 2007, began deployments to Guam. Also, Andersen Air Force Base first planned to have four to six RQ-4 Global Hawk unmanned aerial vehicles (UAVs) for an Intelligence, Surveillance, and Reconnaissance (ISR) Strike Task Force by 2009, but the first of three RQ-4 Global Hawks arrived in September 2010. Andersen also plans to host the MQ-4C Broad Area Maritime Surveillance Triton drones in 2017. The Chief of Naval Operations (CNO), Admiral Jonathan Greenert, explained in November 2012 that the strategic rebalancing of priorities and expansion of air surveillance operations involve the operation of the Navy's MQ-4 Global Hawk UAVs from Guam by the middle of the decade. Facing the Democratic People's Republic of Korea's (DPRK's) announced threats against Guam in March 2013, the Defense Department announced on April 3 that it would deploy to Guam within weeks a Terminal High Altitude Area Defense (THAAD) ballistic missile defense system as a precautionary measure to improve defenses against the DPRK's missile threat. Originally, the United States and Japan agreed in October 2005 to realign the U.S. force posture, in part to sustain the alliance and meet the needs of the changing security situation.