Military planners say there is a "realistic possibility" that RAF bases in Suffolk could be hit by a terrorist bomb or biological attack.
RAF Mildenhall in Suffolk is a major US base in the region
This follows an exercise involving emergency services in Suffolk, Norfolk and Cambs and the US Air Force, looking at how to deal with an attack.
The operation at RAF Mildenhall, Suffolk, firstly looked at how to respond to a chemical or nuclear bomb.
Secondly it looked at how to deal with illnesses caused by a biological agent.
A spokesman for the 100th Air Refueling Wing at RAF Mildenhall, which led the exercise, said: "Because there is a realistic possibility of such catastrophes, the exercise proved very valuable in working through significant details on several issues."
The exercise, which aimed to identify any possible shortfalls in preparation, also involved the medical teams at RAF Lakenheath in Suffolk.
British agencies involved in the exercise included: the Ministry of Defence Police, Suffolk and Norfolk Police, East Anglian Ambulance Trust, the Health Protection Agency (HPA) and the Suffolk Health Emergency Resilience Team.
Dr Mark Reacher, East of England regional epidemiologist with HPA, said the exercise, which took place earlier this month, was useful because the scenarios were realistic.
"We know who to contact here. We will have early conversations in the event of an incident."