A significant military escalation?

Citing civilian satellite imagery, US broadcaster Fox News reported on February 16 that the Chinese military has deployed an advanced surface-to-air missile system to one of its contested islands in the South China Sea. The report, which was based on pictures from ImageSat International, said the missiles appeared to be the HQ-9 air defense system.

US officials and Taiwan's defense ministry were later quoted as saying that the missile batteries had been set up on Woody Island in the Paracels. China has controlled all of the Paracels, which are also claimed by Vietnam and Taiwan, since the mid-1970s and the end of the Vietnam War.

Chinese Foreign Minister Wang Yi sought to downplay the reports, accusing the media of hyping the issue. But Admiral Harry Harris, commander of the US Pacific Command, told reporters such a move would represent "a militarization" of the disputed waters in ways that Chinese President Xi Jinping said he would not do.

In a DW interview, Neil Ashdown, deputy editor of IHS Jane's Intelligence Review, an online, print, and digital security publication, talks about HQ-9's capabilities. He also outlines why he believes they were deployed to Woody Island and what the move reveals about Beijing's South China Sea policy.

DW: China has said that any deployment of missiles on its own territory would be legitimate. Why would China deploy such missile batteries at this moment in time?

Neil Ashdown: It is probable that the deployment was intended to send a message to the United States and other claimants in the South China Sea, in the wake of freedom of navigation operations conducted by US naval vessels in October 2015 and January 2016.

The message is that China is capable of defending its territorial claims to these islands and reefs, with the implication that it is also serious about pursuing its less well-defined maritime claims in the South China Sea more broadly. It also established further facts on the ground ahead of any ruling by the Permanent Court of Arbitration (PCA) in The Hague on China's maritime claims in the South China Sea, expected in June 2016.

If China has indeed deployed such an advanced surface-to-air missile system, why would it choose Woody Island in the Paracels and not, say, one of the Spratly Islands?

The Paracel Islands are closer to mainland China than the Spratly Islands, which Beijing may see as making the deployment less provocative. While significant land reclamation work has taken place on Woody Island, it is also undisputably an island for legal purposes, meaning its status is less contentious than some of the features that China has expanded in the Spratlys, for example Subi Reef, which was submerged at high tide before the reclamation work took place.

Fox News says the missiles appear to be the HQ-9 air defense system. What is this system capable of?

The HQ-9 is a fourth-generation surface to air missile (SAM) system. While not the most advanced SAM system in the world, if it has indeed been deployed to Woody Island then this would be the most advanced long range air defense missile currently deployed to an island in the South China Sea.

The HQ-9 is capable of engaging multiple aircraft, including combat aircraft. It resembles the Russian S300 system but China is assessed to have developed variants of the system with a longer range, potentially up to 230 kilometers.

What strategy is China following here?

The deployment is in line with China's strategy of creeping militarization in the South China Sea. Under this strategy, China uses diplomatic and military activities by rival claimants and the United States to justify increasing the number and effectiveness of military systems deployed to the islands. For example, over the course of 2015, China began preparations for placing short-range air defense systems on islands in the Spratlys.

IHS Jane's satellite imagery analysis of the Chinese-controlled Cuarteron Reef in the Spratly islands in January 2016 showed that China had constructed platforms that could potentially be used for such short-range defensive weapon systems.

That said, if China has indeed deployed a fourth-generation SAM system to the South China Sea, then this would represent a significant military escalation on its part, leapfrogging steps such as deploying shorter-range systems and increasing the tempo of visits by military aircraft to the islands.

However, the deployment is still less significant from a military perspective for the US and others than the deployment of systems such as the YJ-type anti-ship cruise missiles.

How are neighboring countries and the US likely to react?

In the short-term, the US and other claimants (including the Philippines and possibly Vietnam) are likely to criticize the move and accuse China of militarizing the South China Sea, a charge that Beijing will deny.

Looking beyond this, the deployment - if confirmed - would indicate that China is planning to take a stronger line on its maritime claims in the South China Sea in 2016 than it did in 2015. This will complicate regional diplomacy, particularly around the PCA ruling expected in June, with regional states in particular likely now to question the extent to which they are willing to vigorously pursue disputes with Beijing.

Neil Ashdown is Deputy Editor at IHS Jane's Intelligence Review.

The interview was conducted by Gabriel Domínguez.