A capable sovereign submarine capability is a core requirement for Australia’s defence over the next two decades. ‘Sovereign’ in this sense means under Australia’s national control. Australia’s ‘Optimal Pathway’ to acquiring and maintaining a nuclear-propelled, conventionally armed submarine capability from the 2030s and beyond has been agreed by all three AUKUS nations.

This report outlines that the Optimal Pathway has significant cumulative risk involved. There are three major complex enterprises that must all align if Australia is not to experience a serious gap in its sovereign submarine capability in following this path:

• the Collins-class life-of-type extension (LOTE)
• the transfer of three or more Virginia-class nuclear attack submarines (SSNs) from the US
• Australia’s construction – with UK and US assistance – of the SSN-AUKUS, which is to be a new class of SSN submarines for the Royal Australian Navy (RAN).

To assist in managing these three areas of separate but compounding significant risk, this report proposes that Australia should explore the backup option of leasing or otherwise rapidly acquiring small numbers of an advanced conventional submarine capability from Japan.