Fighter jets from the US and two key allies roared into western Pacific skies in the combat phase of annual exercises that have gained importance as the region responds to the rise of China and other potential threats.
The Cope North drills which could soon swell in participants are aimed at preparing air forces of the US, Japan and Australia to fight together if a military crisis erupts.
They also send a vivid reminder to Beijing that America's regional alliances are strong, though officers leading the maneuvers say they are not looking to bait the Chinese military.
"The training is not against a specific country, like China," Japan Air Self-Defense Force Lt. Gen. Masayuki Hironaka said. "However, I think (the fact) that our alliance with the US and Australia is healthy is a strong message."
The three allies began flying sorties together earlier in the week around the US territory of Guam in a humanitarian phase of the exercises, dropping emergency assistance in packages that wafted down under parachutes to jungle airfields.
Yesterday, fighter jets were joined by bombers, transport planes and tankers that refuel the fighters in midair. For the first time, Japanese tankers were joining the drills.
US officials said they believe more allies, particularly New Zealand and the Philippines, will join the exercises soon. Maneuvers like Cope North are a key element of Washington's evolving strategy in the Pacific as the US shifts its emphasis away from Afghanistan and fighting ground wars.
It is now placing more attention on Asia and the possibility of an air or sea confrontation with the rapidly modernizing Chinese military, which has been briskly improving its forces and using its growing muscle to back up territorial
claims that have raised regional tensions.
This "Pacific rebalance" will bring newer and more advanced aircraft and ships to the Pacific theater over the next several years and spread out the tens of thousands of US troops now primarily based in Japan and South Korea.
US Marines have already begun rotational deployments to Darwin, in northern Australia, and about 9,000 Marines stationed on the southern Japan island of Okinawa are to be moved to this tiny island, Hawaii and other locations.
The changes reflect a deepening strategic concern over the rise of China as a regional military power with the potential to challenge Washington's ability to intervene in a crisis, particularly around Taiwan or islands in the south and east
China seas that are contested by China and