On September 30, the destroyer USS Decatur sailed into waters close to China's Nansha Islands without permission from the Chinese government. This is the latest move for the US to show military muscles in the South China Sea under the pretext of "freedom of navigation and overflight."

The operation comes at a tense time when Beijing and Washington are confronting each other in a trade war that has seen them impose increasingly severe rounds of tariffs on each other's imports.

The move also coincides with a time of escalated tensions between the two militaries. China recently denied a request for a US warship to visit Hong Kong and this month China also suspended or postponed some military-exchange programs in protest against a US decision to impose sanctions on the Equipment Development Department (EDD) of the Central Military Commission and its director for buying Russian military equipment.

Those factors combine to lead to a suspicion that the confrontation between Beijing and Washington is expanding beyond trade to military and potentially getting out of control.

The suspicion is also doubled by some tactical details of this latest Freedom of Navigation (FON) operation. Unlike the previous FON operations conducted in the South China Sea, the US side in a rarely seen tone blasted PLA Navy's response as “aggressive” and in an "unsafe and unprofessional maneuver."

“The PRC destroyer approached within 45 yards of Decatur's bow, after which Decatur maneuvered to prevent a collision,” the US Pacific Fleet spokesman Charlie Brown said on Monday.

For its part, the Chinese side strongly urges the US side to immediately stop provocative operations that is “seriously threatening China's sovereignty and security” and “seriously undermining the relations between the two countries and the two militaries.”

While it is natural to link the latest US move in the South China Sea with the on-going trade war between the two sides as their military strains are locked in an increasingly heated trade war, it is still too early to draw hasty conclusions on a worsened and potentially out-of-control prospect of military ties between the two sides.

First, it is not the first time that the US conducts FON operations in the South China Sea, and neither is it in the South China Sea where the US conducts FON operations against China.

Based on materials of US DOD Annual FON Reports available on its State of Department websites, even long before the Obama administration publicized its first FON operation when the USS Lassen illegally entered waters near relevant islands and reefs of China's Nansha Islands, the US has long been conducting FON operations in the Yellow Sea, the East China Sea and the South China sea since 1986 to protest against various Chinese maritime claims.

FON operations are part of the broader US FON Program, which represents a long-standing US policy. Not only aiming China, the US also used this tool to challenge excessive maritime claims of its allies. The coincidence between the latest FON operation and the trade war does not necessarily enable it as one part of the trade war.

Second, an often-neglected fact is that the Trump administration has reformed the way of planning FON operations by approving a package deal for the whole year when US Navy ships will sail through waters China claims. This is different from the practice of the Obama administration where the FON operations are approved on case-by-case studies.

The change of the ways of planning operations not only speed the approval procedure of one particular FON operation but also make it less influenced by the political considerations of that particular time. It also implied that the latest FON operation might have been approved even before the embarkment of the trade war.

Looking back upon the history of Sino-US relationship, ups and downs are quite often seen correspondent with crises and normalizations. Looking forward, there is a reason to believe that dialogue and cooperation between the two largest economies is the only possible way out of the current crisis. A worsened military ties out of control between the two nuclear powers will lead to nowhere and pay an unbearable price for peace and security of both the two peoples and the whole world.

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