Jason Robertson/US Air Force
US drills with Australia and Japan in the Pacific will include air-combat exercises designed to improve their ability to use smaller airfields in case major bases are attacked.
US commanders believe there is a growing threat to its military facilities from China's and Russia's missiles and bombers.
The United States is conducting a joint exercise with Australia and Japan on Guam as it seeks to counter its increasing vulnerability to attack from Russia or China.
The joint exercise at the Andersen Air Force Base, known as Cope North 2021, started on Wednesday and will run until February 19 and will see the base hosting F-35A joint strike fighters for the first time.