On Sunday, a Chinese Type 052C destroyer confronted the U.S. Navy destroyer USS Decatur in the international waters of the South China Sea. The Chinese-flagged warship attempted to assert China’s sovereignty over the waterway by crossing the Decatur’s bow in a maneuver U.S. Navy officials characterized as “unsafe and unprofessional,” forcing the Decatur to take evasive maneuvers to prevent a collision.

“At approximately 0830 local time on September 30, a PRC LUYANG destroyer approached USS DECATUR in an unsafe and unprofessional maneuver in the vicinity of Gaven Reef in the South China Sea,” said Capt. Charlie Brown, a U.S. Pacific Fleet Spokesman. “The PRC destroyer approached within 45 yards of DECATUR’s bow, after which DECATUR maneuvered to prevent a collision.”

However unusual it may be for nations’ warships to square off in such a manner, this incident is far from isolated as it pertains to Chinese aggression throughout the waterway. The South China Sea is both incredibly resource rich and an integral global shipping lane, seeing an estimated one-third of global commerce travel across its waters. At least five nations have competing claims over portions of the waterway, but only China has attempted to lay claim to all of it. The United States, despite not having a sovereign claim over any portion of the South China Sea, has also maintained a presence, tasked with supporting regional allies and, as was the case in this past week, enforcing agreed upon norms over international waters.

China claims there are no international waters anywhere in the South China Sea and has asserted ownership of the waters and airspace through military posturing. They then release statements through government-owned media channels that characterize any foreign presence as attempts at imperialism, often accusing the US of being the aggressor for traveling through shipping lanes seen by the international community as free for any to pass through. Their rapid naval expansion and aggressive behavior has drawn the attention of more than one of the globe’s naval powers as a result.

“We would view any use of ­intimidation or aggressive tactics as destabilizing and potentially dangerous,” Australian Defense Minister Christopher Pyne said, regarding China’s behavior on Sunday. “Australia has consistently expressed concern over ongoing militarization of the South China Sea and we continue to urge all claimants to refrain from unilateral actions that would increase tension in the region,” he added.

Last month a Royal Navy  amphibious transport ship, the HMS Albion, was also warned by Chinese military officials for traveling through the international waters of the South China Sea, calling its presence a violation of “China’s territorial sovereignty,” because of its proximity to man-made and militarized Chinese islands dotting the middle of the waterway, rather than an encroachment on Chinese shores.

“China strongly urges UK to immediately stop such provocative acts that damage the overall situation and regional peace and stability of the two countries,” Hua Chunying, a spokesperson for China’s Foreign Ministry, said at the time.

Japan also deployed a submarine to participate in war games in the South China Sea, as well as to visit Vietnamese ports. Vietnam was forced off of its own oil rigs by China after they claimed the installations fell within their sovereign waters (off the coast of Vietnam). France has also deployed warships to the region within the past few months to conduct similar operations aimed at both increasing international cooperation among allies as well as making it clear to China that most of the globe’s most powerful navies don’t acknowledge their claims over the waterway.

“US allies and partners are really stepping up and conducting these operations that you only saw from the US in the past,” Abigail Grace, a research associate in the Asia-Pacific Security Program at the Center for New American Security, told the New York Times last month. “So this broader multilateralism is something that will really impair China’s claims and something that the international community and the US are working strongly on to make sure that it’s not just an American-led effort.”