Iran attacks damage 20 US military sites since start of war, satellite images show

The extent of damage caused to US facilities is difficult to quantify, but a May estimate by the Pentagon put the total cost of Operation Epic Fury at $29bn, external - with much of that likely to be spent on "repair or replacement costs for equipment" destroyed in the conflict. Democrats say this is likely an underestimate.

The report also found that at least 42 aircraft - including F-15 and F-35 fighter jets, 24 MQ-9 Reaper drones and an A-10 attack plane - have been destroyed or damaged since February.

By comparison to the expensive hardware used by the US military, Iran has reportedly made use of cheap, easily replaceable drones in its attacks on targets across the Middle East.

Experts who spoke to BBC Verify said that Iranian tactics had evolved over the course of the war, moving from sprawling barrages of missiles which targeted cities and bases across the Middle East, to more precise, directed attacks.

"[Iran's] opening salvos were optimised for volume—mass waves designed to overwhelm air and missile defences through sheer numbers," said Dr Kelly Grieco, an analyst with the US-based Stimson Centre think tank.

"Within days, however, Iran had shifted to smaller, more precisely targeted salvos, conserving remaining missiles and drones for specific high-value targets and concentrating fire where even near-misses cause significant damage."

An analyst at MAIAR told BBC Verify that the US military "appears to have been guilty of a degree of early-war complacency" in failing to move aircraft out of the range of Iranian drones and missiles as Tehran's tactics evolved.

They said that in the case of Prince Sultan airbase the facility had previously come under fire before the aircraft were destroyed.

Iran's Supreme Leader Mojtaba Khamenei vowed that "the nations and lands of the region will no longer serve as shields for American bases," adding: "America will no longer have a safe place in the region for mischief and the establishment of military bases, and day by day it will drift further from its former position."

His comments came just days before the ceasefire between the US and Iran came under strain again. On Thursday Iran's Islamic Revolutionary Guard Corps (IRGC) has said it targeted an American base in the region, after fresh US strikes on southern Iran.

Dr Grieco warned that should the fragile US-Iranian ceasefire breakdown and fighting resume, the existing damage to US bases suggests that facilities across the Gulf could be vulnerable.

"The current conflict has consumed US and partner air defence stocks at a significant rate," she said.

"There is no rapid path to replenishment, meaning any renewed Iranian assault would be met a fraction of the interceptors available when the conflict stated."

Additional reporting by Barbara Metzler and Tom Gould.