While much of the focus in the Trident replacement debate in the UK is on Britain's long-term role as a nuclear power, a second decision is imminent, concerning the acquisition of two large aircraft carriers. In combination, these two projects will do much to determine the UK defence posture for several decades to come and are therefore best analysed together. The decisions are particularly significant when viewed in relation to the post 9/II US defence posture, especially in what is now being termed the ‘long war’. The new aircraft carriers will make it possible for the UK military to work closely with the United States in future expeditionary warfare, with all the potential political controversies that might result.