The U.S.' newly-reinforced Asia-Pacific alliance has turned out to be an important factor influencing the regional landscape and big power relations.Historically,the close political and military cooperation between the U.S.and its allies was one of the factors that helped it win the Cold War.After the end of the Cold War,and especially during its War Against Terror,Washington' s overconfidence earned it many critics and even some former allies distanced themselves from it.To some extent,this rattled the foundation of U.S.hegemony.After more than a decade of this War Against Terror,the U.S.has turned its strategic focus towards the Asia Pacific,intending to rebalance power in the region and reinforce ties with its allies.Some American strategists have realized that they can't stop a rival alliance forming to challenge its regional influence unless they strengthen American alliances in the region,promote a rule-based International order and launch a Trans-Pacific security system.The U.S.defense strategy is clear about Washington's intention to stand by its allies and friends and that it values existing ties for providing a foundation for maintaining security in the Asia Pacific.