The publication of this compendium could not be more timely as a contribution to the debate which continues in NATO capitals. NATO is an alliance based on consensus. It is also the most effective military alliance in history; this is largely due to the existence of its integrated and multinational command structure. That command structure, the cement of the Alliance as it were, derives from the mutual obligations contained in Article V of the North Atlantic Treaty. This contractual obligation, which does not exist for the other missions which have arisen since 1990, means that the defense of NATO territory must be the basis of any restructuring. If we were to move away from this and thus weaken the command structure, even with the best intentions, then it is my firm conviction that we would do serious harm to the Alliance and its future. On the other hand, a modified command structure, still based on the Article V contractual obligation, provides a firm basis, as well as flexibility, versatility, and availability for any non- contractual, namely out-of-area, requirement. Command structures do not exist of their own accord. They come into being, change, and develop, to permit commanders at the appropriate level, from top to bottom, to orchestrate the application of military force at sea, in the air, and on land. There is, however, a limit to which one can impose responsibilities on commanders, who after all are personally responsible for the conduct of operations, and a limit to the amount of specialization and detail with which they can cope. This is why we have hierarchical command structures with each commander dealing with the appropriate level of competence. It is why at certain levels command should be joint and at others purely functional. How many levels of command are needed will be dictated by the operations factors of time, forces, and space.