Since 2000, the U.S. military has been building up forward-deployed forces on the westernmost U.S. territory of Guam (west of Hawaii) to increase U.S. operational presence, deterrence, and power projection for potential responses to crises, disasters, or other contingencies to support Japan, Republic of Korea (ROK), the Philippines, Taiwan, or others in Asia. Since 2006, joint exercises based at Guam called "Valiant Shield" have boosted U.S. military readiness in the Pacific. The defense buildup on Guam has been moderate. China has concerns, suspecting Guam's buildup to be directed against China. There has been concern that China and North Korea could target Guam with missiles. China's People's Liberation Army (PLA) Navy has increased activities in waters around Guam. Still, Guam's role expanded in engaging with the PLA.