A series of recent security incidents at British military bases used by the U.S. has forced the U.S. government to hastily relocate several aircraft and raise the level of threat faced by some troops.
Twice, in October and November, the United States moved aircraft in response to threats that officials said came from Iran. In separate incidents in October, two Latvian men were arrested at another Royal Air Force (RAF) base used by US military personnel.
The frequency of incidents illustrates both the risks inherent in Britain’s decision to allow the US military to conduct defensive strikes against Iran from its own air bases and the country’s strategic importance as a base for expensive US aircraft, which makes it an attractive target.
The British government insists the base remains secure and says it has strengthened security measures across the site.
So how rare are these cases, and why do they seem to be concentrated in the UK?
No. According to the British government in March, there are about 12,300 U.S. military and defense personnel in the U.K., but a much larger number are based in Germany, home to U.S. European Command. There are about the same number of US troops in Italy as there are in the UK.
Britain may not have the highest number of US troops stationed in the country, but its bases are of great strategic importance and often host very expensive US military aircraft.
RAF Mildenhall is the only U.S. permanent presence in Europe for refueling aircraft, providing critical support to enable U.S. forces to quickly deploy anywhere in the world. Flight tracking data analyzed by CNN shows 10 U.S. refueling planes were moved away from the base on Monday after a threat from Iran was deemed credible, according to a person with knowledge of the information that prompted the evacuation.
The official did not provide details on the nature of the threat to the base, but said that in recent weeks, U.S. intelligence has learned of a wide range of “diverse, broad and specific” plots being discussed by Iranians against U.S. targets.
Fairford Air Force, which was targeted in September, has similar strategic importance. Its long runway means it is one of the few U.S. military bases in Europe that can accommodate all three types of long-range bombers operated by the U.S. Air Force.
Importantly, the United States has used the Fairford to attack Iranian missile bases used to attack ships in the Strait of Hormuz, meaning that American B-1 bombers are stationed in the Strait of Hormuz.
That made him the prime target of a failed plot led by the commander of an Iranian terror proxy from his imprisonment in New York, U.S. federal prosecutors alleged in a new indictment Tuesday.
The plan involved using fuel-filled vans as vehicle-borne improvised explosive devices, people briefed on the plan told CNN.
Louise Kettle, a professor at the University of Nottingham who studies British-Iranian relations, said that as well as targeting American assets, another key objective of Iran’s external attacks has always been to undermine relations between the United States and its allies. In such a case, “the relationship between the US, UK and Israel would be weakened,” she told CNN.
In the months since the US and Israel first launched attacks on Iran, the threat the Islamic Republic poses to Britain has changed. MI5 chief Ken McCallum said the country had changed its strategy to try to expand its hybrid operations and “attack more difficult targets such as military installations”.
Kettle said this reflects a broader shift in Iran’s strategic approach, with the breakdown of Iran’s traditional policy of maintaining a “forward defense pattern” through proxy groups across the Middle East.
“We have to hope that they change their strategy because not only has the UK changed their approach by allowing the US to use their bases, not only has the world situation changed because the US is at war with Iran, but Iran’s strategic capabilities have also changed,” she added.
Just last week, Iranian state media outlet Hamshahari threatened other European bases, including those in Germany, Italy and Greece. The newspaper’s front page featured a mock map of Europe with red pins marking each base it threatened, warning: “Let’s see what happens.”
Mr McCallum said the Fairford incident was “not unique”, adding: “There are other examples, not just in the UK but around the world”, without providing further details.
Still, McCallum noted that Iran’s ability to operate far beyond its borders is largely limited to subcontracting “criminal agents.” As such, its capabilities are limited only to “advanced levels of criminals,” he added, and police and intelligence agencies can currently deal with these threats “quite competently.”
In Britain, the threat has mainly manifested itself in attacks against the Jewish community, dissident journalists, and military bases. However, it may take different forms depending on the country. France, which has no permanent U.S. troops to target, is participating in a “defensive” operation against Iran, but on Monday blamed the Islamic Revolutionary Guard Corps for last month’s cyberattack on supermarket refrigerators that ruined produce at about 700 retail stores, a claim the Iranian government says is “baseless and hostile.”
The unusual nature of the case attracted significant international attention in September when British police were alerted to three suspicious vehicles driving towards Fairford.
However, due to their nature, military bases are always subject to attack. “When you host another country that is at war with another country, obviously (the base) becomes a target for the country that is at war,” Kettle said. “So this is not just a British thing, it’s a standard part of war.”
Back in November 2024, several bases across Europe that house U.S. troops reported seeing small drones flying overhead. Although they were never officially identified, a report by the International Institute for Strategic Studies, a security think tank, assessed that they may have been part of a Moscow-led campaign.
Security at Britain’s bases is “layered and intelligence-led,” the country’s defense preparedness minister, Luke Pollard, said on Thursday. “We combine physical protection, access control, surveillance, security, security, aerial surveillance and counter-drone capabilities. We don’t rely on any single measure.”
