How will Britain’s defense review affect its allies?

When the Labour Party won the U.K. general election in July, it took office having promised wholesale change. Its campaign manifesto, a safe and unthreatening document of generalizations and platitudes, had been stripped of as many promises as possible; one result is that the new government’s reflexive response is “that’s under review.”

However, Labour had said since 2021 that the first task at the Ministry of Defence would be a full-scale Strategic Defence Review.

New administrations tend to conduct early defense reviews: The last Labour government under Tony Blair did so in 1997, David Cameron’s coalition government undertook a review in 2010 and repeated the exercise after the 2015 election, when he parted with his allies and governed as a Conservative.

The new defense secretary, John Healey, announced the current Strategic Defence Review within two weeks of taking over. It has broad terms of reference, to “consider all aspects of Defence, involving and receiving inputs from other Government Departments, agencies and industry, in areas where they support UK Defence,” and the review team will deliver its conclusions and recommendations in the first half of 2025.

The U.K. prides itself on being a staunch and reliable ally of the U.S., and a resolute supporter of NATO, so what difference might the outcome of the review make from Washington’s perspective?

There are some areas outside the review’s scope. The Prime Minister Keir Starmer has made it clear that he is committed to maintaining and renewing the U.K.’s independent strategic deterrent, so the Royal Navy will replace its four Vanguard-class nuclear submarines armed with Trident missiles on a like-for-like basis. The Ministry of Defence also emphasizes that “NATO will remain the cornerstone” of U.K. defense, and its “support for Ukraine is steadfast and will endure for as long as it takes for Ukraine to succeed.”

The central question is spending. The previous government had pledged to increase defense spending to 2.5 percent of GDP by 2030, which would be a larger proportion than 25 of NATO’s 32 members. Starmer has matched this, calling it a “cast-iron commitment.” But he has not set a timescale for it, which makes it meaningless. The chancellor of the Exchequer, Rachel Reeves, has in fact told government departments to find major savings, and in the short term it is widely expected that the Ministry of Defence will receive less money rather than more.

The AUKUS agreement between the U.S., the United Kingdom and Australia should remain in place, as the government has said it is “committed to the delivery” of its terms. Former national security adviser Stephen Lovegrove has been appointed to “maximize the benefits” of AUKUS and “unlock further opportunities.”

One element of AUKUS is that the U.S. Navy will deploy Virginia-class attack submarines to HMAS Stirling in Western Australia as early as 2027, and in theory that commitment will be shared with the Royal Navy’s Astute-class hunter-killers. However, it was revealed last month that none of the five Astutes has completed an operational voyage in 2024, partly because of a shortage of maintenance docks in the U.K.’s three naval operating bases.

A sixth vessel, HMS Agamemnon, is due to enter service next year and the seventh and final boat, HMS Agincourt, should arrive in 2026. Meanwhile, the Pentagon is aware that Britain might struggle to deploy any of its submarines at present, and so it might fall to the U.S. Naval Submarine Forces to fill the gap. Secretary of the Navy Carlos Del Toro called earlier this year for the U.K. to increase its spending and invest more in the Royal Navy.

From the American point of view, that could be a pattern repeated elsewhere in cooperating with Britain’s armed forces. Parliament identified a £17 billion ($22.2 billion) deficit in the 2023-2033 equipment budget and that will get worse. When missile and air strikes were ordered against the Houthis in Yemen, the U.K.’s contribution was only four fighter aircraft based in Cyprus, while the U.S. had a carrier group with an air wing of around 75 aircraft and a cruise-missile submarine in the region.

Britain is committed in principle to the Indo-Pacific region, the Persian Gulf and the Middle East, and to NATO, AUKUS and supporting Ukraine. But the armed forces are overstretched and under-resourced, and recruitment is inadequate. The review cannot reduce those commitments and there is little likelihood of more spending.

The so-called “special relationship” between Britain and America is often exaggerated and sometimes underplayed. The reality in the 21st century has been that when the U.S. takes military action, it would rather do so with others, and Britain is its preferred partner. We have seen that in Afghanistan, Iraq and Libya, in diminishing the Islamic State across Syria and Iraq, and now in the Red Sea and defending Israel. But if all else fails, America will act unilaterally.

The Strategic Defence Review is likely to see Britain trim its ability to project military force. While the Labour government would undoubtedly prefer to see Vice President Kamala Harris win November’s election than manage a second Trump presidency, it will still generally align with the U.S. Whoever occupies the White House in 2025 will still find a “special relationship,” but its junior partner will have less hard power to contribute.

Eliot Wilson is a freelance writer on politics and international affairs and the co-founder of Pivot Point Group. He was senior official in the U.K. House of Commons from 2005 to 2016, including serving as a clerk of the Defence Committee and secretary of the U.K. delegation to the NATO Parliamentary Assembly.