China said the U.S. plan was designed to “harm China” and that Australia risked getting “caught in the crossfire.”

Boots on the ground

Australian forces have fought alongside Americans in every major war of the 20th century. The two countries cooperated closely during World War II: U.S. forces were housed at several air and naval bases in Australia, and Australian combat troops served under U.S.-led allied command. More than 50,000 Australians served in the Vietnam War; at least 500 were killed. Australians also served in Korea, Iraq and Afghanistan. Even after public opinion turned against those wars, Australia's leaders did not abandon their American allies. Most recently, then-Prime Minister Tony Abbott also sent bomber aircraft, 200 special forces and support troops to help halt the advance of the Islamic State.