If China's satellites and spies were working properly, there would have been a flood of unsettling intelligence flowing into the Beijing headquarters of the Chinese navy last week. A new class of U.S. superweapon had suddenly surfaced nearby. It was an Ohio-class submarine, which for decades carried only nuclear missiles targeted against the Soviet Union, and then Russia. But this one was different: for nearly three years, the U.S. Navy has been dispatching modified "boomers" to who knows where (they do travel underwater, after all). Four of the 18 ballistic-missile subs no longer carry nuclear-tipped Trident missiles. Instead, they hold up to 154 Tomahawk cruise missiles each, capable of hitting anything within 1,000 miles with non-nuclear warheads.

Their capability makes watching these particular submarines especially interesting. The 14 Trident-carrying subs are useful in the unlikely event of a nuclear Armageddon, and Russia remains their prime target. But the Tomahawk-outfitted quartet carries a weapon that the U.S. military has used repeatedly against targets in Afghanistan, Bosnia, Iraq and Sudan. (See pictures of the U.S. military in the Pacific.)

That's why alarm bells would have sounded in Beijing on June 28 when the Tomahawk-laden 560-ft. U.S.S. Ohio popped up in the Philippines' Subic Bay. More alarms were likely sounded when the U.S.S. Michigan arrived in Pusan, South Korea, on the same day. And the Klaxons would have maxed out as the U.S.S. Florida surfaced, also on the same day, at the joint U.S.-British naval base on Diego Garcia, a flyspeck of an island in the Indian Ocean. In all, the Chinese military awoke to find as many as 462 new Tomahawks deployed by the U.S. in its neighborhood. "There's been a decision to bolster our forces in the Pacific," says Bonnie Glaser, a China expert at the Center for Strategic and International Studies in Washington. "There is no doubt that China will stand up and take notice."

U.S. officials deny that any message is being directed at Beijing, saying the Tomahawk triple play was a coincidence. But they did make sure that news of the deployments appeared in the Hong Kong–based South China Morning Post - on July 4, no less. The Chinese took notice quietly. "At present, common aspirations of countries in the Asian and Pacific regions are seeking for peace, stability and regional security," Wang Baodong, spokesman for the Chinese embassy in Washington, said on Wednesday. "We hope the relevant U.S. military activities will serve for the regional peace, stability and security, and not the contrary." (See pictures of the most expensive military planes.)

Last month, the Navy announced that all four of the Tomahawk-carrying subs were operationally deployed away from their home ports for the first time. Each vessel packs "the firepower of multiple surface ships," says Captain Tracy Howard of Submarine Squadron 16 in Kings Bay, Ga., and can "respond to diverse threats on short notice."

The move forms part of a policy by the U.S. government to shift firepower from the Atlantic to the Pacific theater, which Washington sees as the military focus of the 21st century. Reduced tensions since the end of the Cold War have seen the U.S. scale back its deployment of nuclear weapons, allowing the Navy to reduce its Trident fleet from 18 to 14. (Why 14 subs, as well as bombers and land-based missiles carrying nuclear weapons, are still required to deal with the Russian threat is a topic for another day.) (See "Obama Shelves U.S. Missile Shield: The Winners and Losers.")

Sure, the Navy could have retired the four additional subs and saved the Pentagon some money, but that's not how bureaucracies operate. Instead, it spent about $4 billion replacing the Tridents with Tomahawks and making room for 60 special-ops troops to live aboard each sub and operate stealthily around the globe. "We're there for weeks, we have the situational awareness of being there, of being part of the environment," Navy Rear Admiral Mark Kenny explained after the first Tomahawk-carrying former Trident sub set sail in 2008. "We can detect, classify and locate targets and, if need be, hit them from the same platform."(Comment on this story.)

The submarines aren't the only new potential issue of concern for the Chinese. Two major military exercises involving the U.S. and its allies in the region are now under way. More than three dozen naval ships and subs began participating in the "Rim of the Pacific" war games off Hawaii on Wednesday. Some 20,000 personnel from 14 nations are involved in the biennial exercise, which includes missile drills and the sinking of three abandoned vessels playing the role of enemy ships. Nations joining the U.S. in what is billed as the world's largest-ever naval war game are Australia, Canada, Chile, Colombia, France, Indonesia, Japan, South Korea, Malaysia, the Netherlands, Peru, Singapore and Thailand. Closer to China, CARAT 2010 - for Cooperation Afloat Readiness and Training - just got under way off Singapore. The operation involves 17,000 personnel and 73 ships from the U.S., Singapore, Bangladesh, Brunei, Cambodia, Indonesia, Malaysia, the Philippines and Thailand. (See "Hu's Visit: Finding a Way Forward on U.S.-China Relations.")

China is absent from both exercises, and that's no oversight. Many nations in the eastern Pacific, including Australia, Japan, Indonesia, South Korea and Vietnam, have been encouraging the U.S. to push back against what they see as China's increasingly aggressive actions in the South China Sea. And the U.S. military remains concerned over China's growing missile force - now more than 1,000 - near the Taiwan Strait. The Tomahawks' arrival "is part of a larger effort to bolster our capabilities in the region," Glaser says. "It sends a signal that nobody should rule out our determination to be the balancer in the region that many countries there want us to be." No doubt Beijing got the signal.

See pictures of President Obama visiting Asia.

See "Why Is China Slowing Its Military Spending?"

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