Keeping their guards In this December 2010 file photo, USNS Tippecanoe (center) refuels Japan Maritime Self-Defense Force Escort Flotilla ships Ikazuchi (right) and Kongo as USS George Washington steams behind during “Keen Sword” US-Japan joint military exercise in the Pacific Ocean. (AP)CAMP KENGUN, Japan: Here's the scenario: A southern Japanese island is under attack and American forces are coming to the rescue. The potential enemy isn't identified on the maps flashing across computer screens, but the elephant in the room is obvious: It's “the big country to the west,” says one US military official. It's China. In keeping with the adage of hoping for the best while preparing for the worst, the US and its Asian allies are boosting their defenses, even after American and Chinese leaders talked up the need for closer ties in two high-profile visits this month. In Washington, Chinese leader Hu Jintao received a pomp-filled welcome usually reserved for close allies. Just before, US Defense Secretary Robert Gates was given similar treatment in Beijing, even getting a look inside China's nuclear warfare headquarters. But largely outside public view, jockeying between the US and China for strategic advantage in the Pacific is intensifying. The US has long been the dominant military power in the region, protecting Japan, South Korea and Taiwan and keeping vital shipping lanes open for trade. China is now emerging as a rival, sending its ships farther out to sea as its military strength grows. An unusual flurry of activity in the past two months reflects the concern over China's rise: – As Gates began his tour, an American aircraft carrier, the USS Carl Vinson, and its battle group were taking part in exercises in the East China Sea, where a diplomatic skirmish broke out last fall between Tokyo and Beijing over contested islands. – The exercises followed a major joint operation with Japan in December – with the USS George Washington carrier group and an amphibious assault ship – to simulate reclaiming a southwestern island and bottling up the Chinese navy. – As Hu concluded his trip, Japan and the US began the ongoing “Yama Sakura” exercises, a mock-up deployment to repel a full-scale invasion of Kyushu, the southernmost of Japan's four main islands. They end Feb. 3. US military officials, speaking on condition of anonymity because of the sensitivity of the issue, confirmed the general outlines of the two naval exercises. The training serves two purposes, said Toshi Yoshihara, an associate professor at the US Naval War College in Newport, Rhode Island. “First, it makes sense for the alliance to send a deterrent signal to China. Second, it is prudent for Washington to reassure Tokyo.” American officials studiously avoid calling China a threat and stress the importance of the recent political overtures. They say the Kyushu exercises are not directed at any particular adversary. “It's like a football scrimmage,” Lt. Gen. Benjamin Mixon, the commander of the US Army in the Pacific, said at the headquarters for the Kyushu exercises. “Somebody's got to wear the red shirts.” But Aurelia George Mulgan, a Japan specialist at the Australian Defense Force Academy at the University of New South Wales, said the recent US-Japan activity “smacks of a new containment policy.”