Kadena Air Base is a United States Air Force base in the towns of Kadena and Chatan and the city of Okinawa, in Okinawa Prefecture, Japan. It is often referred to as the "Keystone of the Pacific" because of its highly strategic location. It is located 650 km (400 mi) off the coast of China and at a distance of 770 km (480 mi) from Shanghai, a major Chinese economic hub. It is home to the USAF's 18th Wing, the 353rd Special Operations Wing, reconnaissance units, 1st Battalion, 1st Air Defense Artillery Regiment, and a variety of associated units. Over 20,000 American servicemembers, family members, and Japanese employees live or work at Kadena Air Base. It is the largest and most active U.S. Air Force base in East Asia.