The four-phase plan has made nuclear arms control experts nervous … here’s why

• Aukus: nuclear submarines deal will cost Australia up to $368bn

In a tripartite deal with the US and the UK, Australia has unveiled a plan to acquire a fleet of up to eight nuclear-powered submarines, forecast to cost up to $368bn between now and the mid-2050s. Australia will spend $9bn over the next four years.

From this year Australian military and civilian personnel will embed with US and UK navies, including within both countries’ submarine industrial bases. From 2027 the UK and the US plan to rotate their nuclear-powered submarines through HMAS Stirling near Perth as part of a push to step up training of Australians.

Embedded personnel and port visits: Australian military and civilian personnel will embed with the the allies’ navies. US nuclear-powered submarines will increase their visits to Australian ports, with Australian sailors joining US crews for training.

Submarine rotations: From 2027 the UK and the US plan to rotate one UK Astute class submarine and up to four US Virginia class submarines through HMAS Stirling.

Sale of US Virginia-class submarines: From the early 2030s – pending approval by Congress – the US intends to sell Australia three Virginia-class submarines, with a potential option for two more if required.

SSN-Aukus: A combination of UK submarine design and US defence technology will contribute to the development of the new SSN-Aukus submarine – intended as the future attack submarine for both the UK and Australia. Both Australia and the UK intend to start building SSN-Aukus submarines in their domestic shipyards before the end of this decade. The first such boat may enter into UK service in the late 2030s, but the Australian navy will receive its first Australian-built SSN-Aukus submarine in the early 2040s.