Dennis C. Blair, chairman of Sasakawa Peace Foundation USA, was commander of the U.S. Pacific Command from 1999 to 2002 and director of national intelligence from 2009 to 2010. Jeffrey W. Hornung is a fellow with Sasakawa Peace Foundation USA.
China’s deployment of surface-to-air missile launchers to the largest island in the Paracels chain has led to a spike in alarmist analysis. China’s provocative act is being portrayed as a watershed indicator that it is bent on military dominance of the South China Sea. 
It is important to understand the facts and history to identify the true concerns.
First, facts and history: Satellite images of Woody Island in the Paracels from early February showed the HQ-9 air defense system deployed there for the first time. Woody Island is in the northern section of the South China Sea. It is about 250 miles southeast of Hainan Island and 500 miles north of the Spratly Islands that China has enlarged by land reclamation. Unlike the Spratly Islands, which are contested by multiple states, the Paracel Islands are claimed by only China (and Taiwan) and Vietnam. Woody Island itself has been controlled by Beijing for decades and has been heavily built up with civilian and military structures. In any impartial arbitration, China would have a strong claim to this island.
Woody Island has long been home to surveillance radars, an airfield and shelters for military aircraft. Late last year, China deployed advanced jets there and it has apparently done so again in the past few days. According to U.S. Pacific Fleet Commander Adm. Scott Swift, this is at least the third time that antiaircraft missiles have been deployed to Woody Island, although previous deployments were of less advanced systems. On the previous occasions, these deployments were part of exercises, which may or may not be the case in this instance. 
Last year during his visit to Washington, President Xi Jinping stated that China did not intend to militarize the islands it had enlarged in the Spratlys. The missile and aircraft deployments to Woody Island do not violate that pledge.
These deployments do not in themselves affect any of the important U.S. interests in the South China Sea: They do not increase the threat to U.S. freedom of navigation and flight; they do not bring another island under China’s control by non-peaceful means; they do not threaten international shipping in the sea; they do not protect Woody Island from destruction by the United States during a military crisis or conflict.
So why all the concern?
There are two well-founded concerns about the Chinese action: timing and precedent. First, timing: Whether the air-defense and jet-fighter deployments are a long-planned exercise or the beginning of a permanent presence, they belie China’s professed commitment to peaceful solutions to conflicting claims in the region. They are the latest in a line of closely spaced Chinese actions that undercut and contradict Beijing’s soothing words about their aims. Countries with peaceful intentions do not enlarge islands with military-capable airfields, harbors and logistics facilities at a breakneck pace in one part of the South China Sea, then deploy advanced missiles and jets to another part. Second, precedent: If China conducts deployments like this to the islands it has enlarged with runways in the Spratlys, it will violate Xi’s pledge and introduce an air control capability that ratchets up the military stakes in an area of the South China Sea far from China’s borders.
There is a final point that all the excited commentary misses. These deployments and the reaction to them throughout Southeast Asia highlight the self-defeating aspects of China’s aggressive policies. By its small-scale tactical military deployments on indefensible islands in the South China Sea, China is antagonizing all the other littoral countries, which are building their own defenses and turning to the United States and Japan to offer access to their ports and airfields, to increase military cooperation and to request additional security assistance. China’s strategic position in the region is much weaker now than it was six years ago, before it embarked on its truculent and aggressive policies. Meanwhile, to the north, China is unable to restrain its client North Korea. The result is to solidify South Korean, U.S. and Japanese policies and cooperation. 
Finally, China’s economy is sliding. China looks less like a shrewd, confident and successful regional power bent on hegemony and more like a flailing and blustering collection of bureaucrats continuing short-term, outmoded policies to the detriment of their country’s larger interests.