The United States urgently withdrew a dozen B-1 bombers from RAF Fairford in Gloucestershire over the weekend over fears that Iran was planning a complex drone attack on the base, US and European officials told The Wall Street Journal. The Pentagon confirmed the bombers returned to home stations in the US.

Officials told the Journal that a branch of Iran’s Islamic Revolutionary Guard Corps recruited British citizens to carry out the plot, which involved a diversion nearby and drones swarming the airfield to target aircraft and personnel. President Trump said on Monday: ‘They didn’t fly out by accident.’

The move followed the arrest of six people, including five British nationals and one dual UK-Iranian national, near the base on suspicion of preparing terrorist acts. They were later released on bail. British Prime Minister Andy Burnham said there were ‘strong indications’ that Iran was involved, TBS News reported.

Secretary of State Marco Rubio initially called the move part of ‘regular rotations,’ but Trump confirmed it was driven by a threat. RAF Fairford, about 90 miles west of London, has been used for US strikes on Iran since the war began in February. Iran has denied involvement in any plot.