The DPC was the ultimate authority within the Alliance on all questions related to the Alliance's integrated military structure. It effectively had the same level of authority as the North Atlantic Council (NAC) and the Nuclear Planning Group on matters within their competence.
It implemented decisions taken by the participating countries in relation to collective defence planning and issues pertaining to the integrated military structure of the Alliance. It also approved force goals and ministerial guidance for future NATO defence planning.
Although its work focused on the integrated military structure and military and defence related issues, the NAC also discussed some of these matters before entirely taking over the DPC’s responsibilities in 2010. Conversely, in 2003 at the outbreak of the Iraq crisis, the Council moved the decision to authorize NATO military authorities to implement defensive measures to assist Turkey to the DPC.
This was the result of a disagreement among member countries on whether deterrent and defensive measures should be initiated and, if so, at what point? Three member countries - Belgium, France and Germany - felt that any early moves by NATO could influence the ongoing debate at the United Nations Security Council in regard to Iraq and the effort to find a peaceful solution to the crisis.
On 16 February 2003, with the cohesion of the Alliance under strain, Lord Robertson, the then Secretary General of NATO acting in his capacity as Chairman, concluded that no further progress on this matter could be made within the Council.
On the same day, with the concurrence of all member countries, the matter was taken up by the DPC. At the time, it was composed of all member countries, except France, which did not participate in NATO's integrated military structure. The Committee was able to reach agreement and on 19 February 2003 it authorized the military authorities to implement, as a matter of urgency, defensive measures to assist Turkey under the name of Operation Display Deterrence.