In a ceremony at NATO's northern European command headquarters, US General James Jones, the alliance's top military chief, handed over the colours of the new force to its first commander, British General Jack Deverell.
"The passing of the colours... to General Deverell will mark what I consider to be one of the most important changes in the NATO alliance since the signing of the Washington Treaty," which founded the North Atlantic Treaty Organsation in 1949, Jones said.
The NATO Response Force (NRF) represents "an unambiguous commitment of the alliance's intent to stay militarily relevant in a global context", the US supreme commander added.
"For the first time in its history the alliance will have a joint/combined air, land and sea and special operations force under a single commander."
US ambassador to NATO Nicholas Burns said the NRF was "an important, innovative new military capability for NATO, and further evidence of NATO's on-going transformation to meet the new threats from global terrorism".
The force, designed to deploy to hotspots around the globe within five days, will eventually total 21,000 troops when it reaches full capacity in
The contingent represents a radical departure for the 54-year-old alliance from its roots as the West's protector from the Soviet threat.
It also comes only two months after NATO began its first-ever "out of area" mission beyond Europe by taking command of the International Security Assistance Force (ISAF) in Afghanistan.
The UN Security Council voted unanimously this week to allow ISAF to expand its mandate beyond the Afghan capital Kabul.
US proposals to launch the NRF were approved at a landmark NATO summit in Prague in November, at which the alliance also formally approved its expansion from 19 to 26 nations next year.
NATO's enlargement further into eastern Europe will mark another evolution as the alliance tries to stay relevant in the post-Soviet world by adapting to the role of firefighter in global crises.
The NRF's potential on the ground was tested last week at a meeting of NATO defence ministers in the US city of Colorado Springs, in a fictional scenario involving a terrorist threat in 2007 in the Red Sea.
While the military commanders are trigger-ready to deploy wherever and whenever needed, one potential problem may be in taking the political decision to send the force into a crisis.
NATO works by consensus, so any decision must be agreed by all member states. In some countries national parliaments must authorize any foreign deployment of troops.
In Colorado Springs, ministers agreed to study ways of speeding up this decision-making process, with results expected by December.
In an annual report released Wednesday, the London-based International Institute of Strategic Studies said the NRF "will give the alliance the capability to project force rapidly in strength over distance".
But the report warned that NATO must come up with new ways of making decisions if it is "to have credibility in the future as it reforms and defines new structures and missions".
The response force is being drawn from 14 countries, with Spain providing the largest initial contingent of 2,200 troops.
France, which is not part of NATO's integrated military command, has offered 1,700 personnel and aircraft including one AWACS radar surveillance plane.