160. Thirdly, we need to be able to generate forces should the risk re-emerge of General War. This Mission Type has a number of features which distinguish it from the others: we judge it at present to be an extremely unlikely contingency against which we would have a lengthy warning time, allowing us to generate forces through the mobilisation of Reserves; and it would require a military response markedly different in type and scale from all other potential calls on British forces. Its unique demands on our force structure are therefore treated separately.
161. Our force structures are based on a number of key judgements derived from our overall defence and security policies. The first is the key role that NATO will play in developing the military aspects of the response to future challenges. For nearly 50 years, NATO has been the means by which we have successfully maintained our collective defence. It will remain the irreplaceable guarantor of our mutual security and that of our Allies. The foundation of our defence planning remains the ability to respond through NATO were a strategic or regional threat to our interests or those of our NATO Allies to arise in future.