Middle East leaders expect the US to follow through on its military build-up to strike Iran but experts warn that the duration of any campaign will be limited by constraints on Washington's arsenal.
Launching the Military Balance report at London's International Institute of Strategic Studies, Emile Hokayem, senior fellow for Middle East security, said expectations were focused on the US firepower assembled around Iran.
Additionally, indications are that Iran would fight back at a larger scale than during the 12-day war against US ally Israel last June, towards the end of which Iranian nuclear bases were hit from the air by American bombers.
"The region seems to expect a war at this point and [many are] really hoping that the US has thought through the second and third-order consequences," Mr Hokayem said.
"There is a lot of apprehension at this stage because the expectation is that this time it would be bigger and Iran would have a greater incentive to hit at US facilities in the region but perhaps [also] at Gulf infrastructure."
The Military Balance said the US was thought to have "used 150 THAAD interceptors, reportedly nearly 25 per cent of its stockpile" during the 12 days.
Douglas Barrie, senior fellow for military aerospace, said the US has the ability to launch an assault on Iran if it abandons the nuclear talks due between Tehran and Washington in Geneva later this week.
He pointed out that in the event of Iranian missiles being launched, a vital role could be played by US interceptors, which are "protection against Iran's ballistic missile arsenal".
Mr Barrie said of last year’s skirmish: "It was interesting to note just how high the expenditure rate in interceptors was and I think that is something that will be in the back of the mind."
With the imminent deployment of the USS Gerald Ford within strike range, Washington has now two aircraft carrier groups in the region. US President Donald Trump has warned Iran his "armada" is ready to attack if Tehran does not make concessions to his negotiators in the wake of last month's public demonstrations throughout Iran.
Global splurge
The US and Europe are each posting double-digit increases in defence spending in a bid to outstrip spending by adversary nations, four years since the start of the Ukraine war.
The Military Balance report questioned whether the US move to spend more than $1 trillion on defence in 2026 was sustainable year on year.
The closely monitored report said that in 2025, global defence spending reached $2.63 trillion, up from $2.48 trillion the previous year.
It added that while there had been a drop in US defence spending last year, the Trump administration's budget request of $1.01 trillion was a boost of 13.4 per cent.
A big part of the increase is driven by the Golden Dome missile defence initiative and a greater military role for border security.
The jump above the trillion dollar threshold would be difficult to sustain in Congress, the report added.
“The process to achieve the trillion-dollar budget was more complex than in previous years because it used two legislative mechanisms,” it said. “There have been widespread concerns that such levels cannot be sustained.”
Despite global instability, worldwide defence spending had risen by only 2.5 per cent year on year in 2025.
Europe bucked that trend with its regional defence spending growth hitting 12.6 per cent, matching the rate of increase in 2024.
Much of the recent growth was driven by increases in the German defence budget, “where annual uplifts have averaged 21 per cent in real terms since 2022”, the report added.
In raw numbers, the continent’s defence spending grew by almost $100 billion to nearly $563 billion over the course of 2025, more than double the total in 2016.
Europe accounts for more than 21 per cent of the global total compared to 17 per cent in 2022.
The Military Balance report found that growth in Russia’s military expenditure had eased to 3 per cent in real terms in 2025. This followed a 56.9 per cent jump the previous year. Moscow's annual expenditure on military activity is running at 7.3 per cent of its GDP.
IISS researchers concluded that defence spending across the Middle East and North Africa grew by 4.5 per cent in real terms last year. The region is believed to spend almost $219 billion on defence annually.
The Israeli war in Gaza plus “wider regional instability” boosted defence spending to an average of 4.3 per cent of GDP in 2025, up from 3.5 per cent in 2022, the report said.
Algeria was the major driver of higher defence spending last year, shelling out 8.8 per cent of its GDP, second globally only to under-siege Ukraine.
