The US challenge in South China Sea

On October 26, the American missile destroyer Lassen sailed within 12 miles of a Chinese-built artificial island called Subi Reef, in the South China Sea. The goal, according to the US, was to challenge China';s claims over what are generally understood to be international waters.

China was furious. A spokesperson said the Lassen "illegally entered" the waters and "threatened China’s sovereignty and security interests." On Tuesday, China sent two ships — the missile destroyer Lanzhou and patrol boat Taizhou — to the area and told the American ship to get out. The Americans ignored them.

This tension isn';t going away: The US plans to send even more naval patrols into contested South China Sea waters in the coming days. "There have been naval operations in that region in recent days, and there will be more in the weeks and months to come," Secretary of Defense Ash Carter said during a Tuesday Senate hearing.

To understand why all this is happening and where it';s going, you need to understand the backdrop. China is claiming important chunks of territory in the South China Sea, making its neighbors really nervous. America is taking the neighbors'; side, but not just because it wants to side against China. It (the US action) is a practical demonstration that the United States will not accede to maritime claims that violate international law. The South China Sea is one of the tensest places in East Asia.

The sea is resource-rich, full of valuable gas and fisheries and home to critically important trading routes. Six different countries — China, Taiwan, Brunei, Malaysia, Vietnam, and the Philippines — claim territory there. China is, of course, the largest and strongest of those countries by far. As China';s military and economic power has grown, it';s become more assertive about its claims in the South China Sea.

One of China';s tactics has been to build "sandcastles": small artificial islands that it builds in the middle of the sea by reclaiming reefs. International law allows countries to claim waters up to 12 nautical miles off territory they control, so China';s goal here is to claim the water near its new landmasses. It also sometimes turns the islands into airstrips or places mobile artillery on them.

The United States doesn';t formally take a position on South China Sea disputes. But there are lots of reasons America would challenge Chinese island-building claims. This is about both reassuring America';s traditional allies and building partnerships with other nations threatened by Chinese assertiveness. So far, China hasn';t done much to challenge the American moves besides condemning it and moving naval assets nearby.

No one is warning about any real risk of military conflict. But this does represent a new US commitment to the South China Sea. The United States is clearly sending a message to Beijing that it is concerned about its island-building campaign and is more willing than ever to do something about it.

By Zack Beauchamp