The United States Navy has been conducting regular Freedom of Navigation operations throughout the South China Sea for years now, pressing China’s aggressive claims of sovereignty over the entire expansive waterway extending thousands of miles from Chinese shores. Many nations have competing claims over portions of the South China Sea, with much of the international community unified in their assertion that the breadth of the waterway remains “international waters.”

A nation’s sovereign waters traditionally extend only 12 nautical miles from its shores.

Now, America’s closest ally also finds itself at odds with China’s attempts to assert its dominance over the region, laying claim to its rich natural resources and potentially looking to leverage their control over the massive amount of international commerce traveling through the South China Sea at any given time. An estimated one-third of all goods sold anywhere in the world traverse the increasingly contested waterway at some point, making the stakes in China’s staring contest with the rest of the world far greater than mere bragging rights.

Last week, the British amphibious warship HMS Albion passed somewhere near the Paracel islands, which are manned by the Chinese military despite contesting claims over the land masses made by both Vietnam and Taiwan. Reports vary regarding what level of proximity the HMS Albion, carrying a contingent of Royal Marines Commandos headed for Ho Chi Minh City, came to the islands.  Some suggest that they remained outside the traditionally accepted 12 nautical mile limit.  But China’s claims extend well beyond that barrier, and Beijing responded by dispatching at least one People’s Liberation Army-Navy frigate and two helicopters to intercept the British vessel.

“The relevant actions by the British ship violated Chinese law and relevant international law and infringed on China’s sovereignty,” the Chinese government said in an official statement released soon thereafter. “China strongly opposes this and has lodged stern representations with the British side to express strong dissatisfaction.”

“China strongly urges the British side to immediately stop such provocative actions, to avoid harming the broader picture of bilateral relations and regional peace and stability. China will continue to take all necessary measures to defend its sovereignty and security.”

Recently, the American and Japanese navies have also been very active in the South China Sea. They’ve participated in joint military exercises that publicly are for the purpose of increased interoperability between regional forces but also serves as a means to poke at China’s expansive claims over the waterway. The U.K.’s willingness to get involved comes with some diplomatic complications, including a trade deal Britain has been seeking with China to ensure the nation’s financial stability post-Brexit.

“HMS Albion exercised her rights for freedom of navigation in full compliance with international law and norms,” a spokesman for the British Royal Navy told the media after the confrontation.