Numerous countries have military activity. A lot of times we tend to focus on US military moves, such as placing more ships in the Pacific Ocean in order to help out countries such as the Philippines, which is currently fighting with China.
Vietnam is also fighting with China, but it is less inclined to take help in the form of US military moves, given the tensions from the 70s. China is trying to establish a military garrison in the South China Sea. Currently Vietnam and the Philippines are in a dispute over the water rights, especially since China is trying to gain control in order to have command over the oil discovered in the sea. Both countries believe China is trying to “violate international law” by putting the garrison in the South China Sea.
They are looking at the Paracel Islands, which is one of two archipelagos in dispute between China and Vietnam. Manila is also involved in the dispute with the Spratly Islands. US officials are just watching for now, allowing all three countries to try to come to an agreement. Depending on what move is made, things could escalate enough that outside help is needed.
US military forces are already on the move to make certain that they are in the area should the issue intensify. Oil has always been an area of contention in the Middle East and Asia, especially given the money and power it can supply. China has also been making moves regarding more power throughout the world.