Everything you need to know about the South China Sea conflict - in under five minutes

1. Whose South China Sea is it, anyway?

Taiwan Coast Guard patrol ships are seen during a drill held about 4 nautical miles out of the port of Kaohsiung, southern Taiwan, June 6, 2015. REUTERS/Pichi Chuang

China’s claim to the South China Sea is based in history, dating back to records from the Xia and Han dynasties. China delineates its claims via the nine-dash line, which Chiang Kai Shek advanced in 1947. During China’s republican era, China surveyed, mapped and named 291 islands and reefs in the region.

The United States contends that the South China Sea is international water, and sovereignty in the area should be determined by the United Nations Convention on Laws of the Sea (UNCLOS). UNCLOS states that countries can’t claim sovereignty over any land masses that are submerged at high tide, or that were previously submerged but have been raised above high tide level by construction.

2. Why does China want to control the South China Sea?

Control of the South China Sea would allow China to dominate a major trade route through which most of its imported oil flows. It would also allow China to disrupt, or threaten to disrupt, trade shipments to all countries in East and Southeast Asia - as well as deny access to foreign military forces, particularly the United States.

The floor of the South China Sea may contain massive oil and natural gas reserves. Sovereignty over the region could give China a level of energy security and independence far beyond what it currently possesses.

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3. Who has built what?

Island building in the South China Sea, and construction on existing islands, has been going on for decades, primarily by Vietnam and the Philippines, which have claimed 21 and eight islands, respectively. Vietnam, Taiwan and the Philippines have all stationed military forces on at least some of their islands, but Vietnam, in accordance with UNCLOS regulation, has not put troops on what it calls “floating islands” - those constructed on submerged sandbars, reefs and other land masses.

China has come late to the island building game, but its efforts have been on a scale never before seen in the region. In the last 18 months, China has reportedly constructed more new island surface than all other nations have constructed throughout history. And unlike other claimants, China has, at least briefly, placed military equipment on one of its artificial islands, and officials have said that the government plans to do so again. More importantly, only China possesses enough modern military vessels to protect its claims.

4. What is the U.S. response to the dispute?

The United States had virtually no response to previous building by Southeast Asian countries in the South China Sea, but has vigorously opposed China’s efforts. The U.S. Navy has operated continuously in the region since World War Two and, according to Defense Secretary Ash Carter, has every intention of continuing to do so.

The United States will use its aircraft and naval vessels to assert freedom of navigation in the region, as demonstrated by the recent passage of the USS Fort Worth combat ship and the flight, by a U.S. Navy P-8 Poseidon surveillance aircraft, over the Chinese construction at Fiery Reef.

Beyond freedom of navigation missions, the United States is focused on strengthening regional allies. To do so, it will help boost its allies’ intelligence gathering and surveillance capabilities, and provide them with updated military hardware to counter China’s technical advantages in both quantity and quality. (The Philippines, the recipient of U.S. military assistance and training since World War Two, is sorely lacking in military hardware, having only two very old U.S. Coast Guard cutters with which to respond to Chinese incursions.)

Japan, in close coordination with the United States, is to supply military hardware to the Philippines and Vietnam.

5. What should the world expect next?

The dispute between the United States and China is likely to escalate to some degree. U.S. Pacific Command planners are preparing to sail and fly within 12 nautical miles of areas that China claims as sovereign territory. The USS Fort Worth and a P-8 surveillance aircraft have already operated close by, and while China objected, it did not take hostile action.

However, China has stated that it will defend what it considers its territorial limit. If the Chinese government blinks, it could suffer domestically due to the loss of face for the Communist Party. If the United States wavers, it will risk perpetuating the impression, among U.S. partners and allies, that it lacks resolve in light of its policy in the Middle East, Iraq and Ukraine.

The stakes are high for both sides, as is the risk of a miscalculation. The United States is marshaling major allies in the region to take a role, in the hope that the combined weight of U.S., Japanese and Australian forces will give China pause.