Maritime disputes across the vast South China Sea have ratcheted up in recent years as an increasingly assertive China militarizes disputed islands and confronts its regional rivals over their competing claims in the strategically important and resource-rich waterway.

The South China Sea dispute is a series of maritime and island claims between several sovereign states in the Indo-Pacific region. The countries involved are:

China, Brunei, Taiwan, The Philippines, Vietnam, Malaysia.

The countries have been disputing territory in the South China Sea for centuries, but tension has grown in recent years. The sea is a crucial trade route, with over 21% of global trade, amounting to $3.37 trillion, transiting through these waters in 2016.

The sea is estimated to have 11 billion barrels of untapped oil and 190 trillion cubic feet of natural gas. China’s sweeping claims of sovereignty over the sea have antagonized the other countries.

The most active claimants are Vietnam and the Philippines. Vietnam bases its current claims on 17th-century maps. In 2016, the arbitral tribunal ruled in favour of the Philippines on most of its submissions.

The origins and development of the countries’ respective claims and the development of international law as it relates to the South China Sea are complicated, confusing, and often poorly understood.