In September, President Joe Biden and the prime ministers of Australia and the U.K. announced a new defense partnership, surprising allies and competitors alike.

The initiative, known as AUKUS, infuriated France, which lost out on the sale of submarines worth close to $60 billion, and alarmed China, which sees the pact as a direct threat.

Although AUKUS leaders say their initiative isn’t aimed at any country, in particular, it is clear that the deal was designed to counter Chinese influence and ambitions in the Indo-Pacific region.

The pact centers on an agreement for the U.S. and U.K. to provide nuclear-propulsion technology to Australia, but that is only the tip of a collaboration iceberg between the three countries. Their cooperation goes back decades, and special operations forces have been a key component.