U.S. Army missile defence units have carried out the first ever firing of Patriot surface-to-air missiles in Australia as part of joint exercises with U.S. allies there that are likely to agitate China, which is engaged in its own increasingly aggressive military moves in the region.

Patriot missiles “successfully engaged drone targets” on Friday in what a U.S. military statement described as a “historic first” test of the system in the Shoalwater Bay Training Area in Queensland, Australia, during “Talisman Sabre 21” exercises that run through mid-August.

U.S. officials say the exercises, which include participation of forces from Australia, Japan, New Zealand, Canada, the U.K. and South Korea, aim to demonstrate the ability of the allied forces to move easily around the region in response to threats that may arise from any adversaries.

Stars and Stripes, which first reported on the Patriot firing, emphasized the threat of Chinese and North Korean missiles as an ever-present concern for U.S. and other commanders in the region — noting that as recently as 2017, the North Koreans fired a ballistic missile over northern Japan.

In addition to the North Korean threat, the Pentagon has spent recent years warning of expanding great power competition with China, which has come to feature the establishment by the Chinese military of bases on human-made reefs in disputed island chains in the region.

China’s military recently deployed electronic warning and surveillance aircraft and helicopters on two disputed islands in the South China Sea in what analysts say is a sign that the People’s Liberation Army has begun routine air operations from the bases.

Satellite images obtained show deployments in May and June of PLA KJ-500 airborne warning and control aircraft to Mischief Reef in the Spratly Islands. Other satellite photos showed the stationing of a Y-9 transport aircraft and Z-8 helicopter to Subi Reef in June and this month.

The Biden administration has sought to pick up where the former Trump administration left off with by carrying out U.S. military exercises in the region, while also rallying unity among major democracies of the Indo-Pacific to confront the moves by China’s communist government — most notably through the so-called “Quad” nations that include the U.S., Japan, Australia and India.

The current “Talisman Sabre 21” military exercises in Australia are independent from the Quad push.

A U.S. military press release said the drills involve more than 17,000 participants from seven nations, including Canada, Japan, New Zealand, the Republic of Korea, and the United Kingdom, with India, Indonesia, France, and Germany also sending delegations to observe.

Stars and Stripes quoted U.S. Army Col. Matt Dalton, of Portland, Conn., who oversees air and missile defence units in Japan, including Okinawa, and on Guam, as saying during a conference call that American officials are “trying to demonstrate our ability to quickly move our units around the Indo-Pacific to be able to counter any threat that is out there.”

Col. Dalton emphasized the “ability to move to different locations quickly, set up and establish defence of a particular asset.”

The movement and firing of the Patriot system is likely to draw the most attention.

A U.S. military press release said soldiers “based in Japan and Guam from 38th Air Defence Artillery Brigade, 94th Army Air and Missile Defence Command, successfully engaged drone targets with Patriot missiles as part of TS 21, Australia’s largest military exercise with the U.S.”

“Australian and U.S. Forces combine biannually for Talisman Sabre — a key exercise supporting the Indo-Pacific Pathways initiative to advance a free and open Indo-Pacific by strengthening relationships, building trust and interoperability among allies and partners,” the press release stated.