On 30 May 2026, at the IISS Shangri-La Dialogue in Singapore, Australian Deputy Prime Minister and Minister for Defence Richard Marles announced that Australia will acquire three in-service Block IV-standard Virginia-Class submarines for the first three of its nuclear-powered submarines (SSNs) fleet under AUKUS Pillar I. The decision represents a departure from the 2023 “Optimal Pathway,” under which Australia was expected to receive two in-service Block IVs in 2032 and 2035, and reportedly at least one newly built Block V or Block VII-standard Virginia-class submarine in 2038.

Marles described the move as an important measure to “streamline” Australia’s nuclear-powered submarine acquisition, reducing the complexity of sustainment and workforce training requirements over the period from the 2030s to early 2040s when Australia will operate a mixed submarine fleet (see Figure 1). The new plan reduces the number of submarine types operated from four to three, namely:

  • six conventionally-powered Collins-class submarines (set to retire by the 2040s)
  • at least three in-service Block IV Virginia-class SSNs (due to be delivered in 2032, 2035 and 2038)
  • five SSN-AUKUS (the first to be delivered from the early 2040s).

Figure 1. AUKUS optimal pathway vs revised SSN timeline

The new plan retains the 2023 Optimal Pathway option to buy two additional and new Virginia-Class submarines, “if required,” in 2041 and 2044.

The Block IV SSN is one of the most modern and capable US nuclear-powered submarines designed for extended operations involving intelligence gathering, anti-submarine warfare and launching precision strikes. Requiring a crew of around 132 personnel to operate, the Block IV has a displacement tonnage of around 7,900 tons and can dive to depths greater than 244 metres. Powered by a single General Electric pressured water nuclear reactor and pump jet propulsor, the Block IV can reach speeds of 25 knots. The Block IV deploys two Virginia Payload Tubes, each with six cells for 1,700km range UGM-190 Tomahawk Block IV land attack cruise missiles, and four 21” torpedo tubes for Mk-48 ADCAP torpedoes or mines.

While the Block IV does not feature the larger missile capacity of the Block V and Block VI variants, which are equipped with the new Virginia Payload Module and can carry an additional 28 Tomahawk cruise missiles, it nevertheless retains an undersea technological advantage over adversarial nuclear submarines. For example, China’s Type-093B (Shang III) and SSBN Type-094 (Jin) are assessed to possess comparatively less advanced acoustic stealth technologies and mean they are easier for US and future Australian SSNs to detect.

Australia’s three-boat Block IV Virginia-class fleet will be drawn from the United States’ SSN-792 to SSN-800 cohort, commissioned between 2020 and 2028 — i.e. some are still undergoing construction or sea trials and are yet to be deployed. Should Australia have remained committed to the 2016 submarine program with French Attack-class submarines, the timelines would have been comparable, with both programs projected to deliver submarines from the 2030s.

These in-service Block IV SSNs would enter Australian service having already consumed a portion of their reactor life. While a newly constructed SSN is expected to provide 33 years of service, the in-service boats would have closer to 23 years of operational availability following transfer. Under this scenario, the third Block IV scheduled for transfer in 2038 could reach the end of its service life sometime around 2061, compared with around 2071 under the original plan to acquire a newly built SSN. This compresses the transition period between the retirement of Australia’s Virginia-class fleet and the introduction of SSN-AUKUS by over a decade (see Figure 1), leaving less margin to absorb delays in the SSN-AUKUS submarine program should the government decide not to acquire additional Virginia-Class SSNs in the early 2040s.

The government’s decision may ease pressure on the US submarine industrial base, which has a target production rate of 2.33 boats per year — the rate the US Navy estimates is required to satisfy both US force readiness requirements and AUKUS targets (see figure 2). Currently, US Navy production of Virginia-class submarines remains closer to 1.2–1.3 boats annually.

Figure 2. US attack submarine production timeline

These decisions reflect the capability requirements needed to navigate the Indo-Pacific’s changing undersea military balance in the coming decades. The United States still has the largest number of nuclear-powered submarines in the world, at 71, compared to China with 32. However, between 2021 and 2025, China’s People's Liberation Army Navy (PLAN) surpassed the United States for the first time in both nuclear-powered submarine launches — 10 PLAN boats compared with seven for the United States Navy — and total tonnage added, with approximately 79,000 tonnes entering PLAN service against 55,500 tonnes for the US fleet.