"It is scarcely possible to overestimate the significance of this operation," says Lord Ashdown seated in his office overlooking Sarajevo.
"For Bosnia, it marks a milestone on the route from war towards peace stabilisation and eventually joining the European Union."
Enthusiastic words from the chief international envoy to Bosnia ahead of the deployment of the EU military mission to Bosnia, scheduled to take over from the Nato peacekeeping Stabilisation Force (SFor) on 2 December.
Eufor and Nato will continue to hunt for war criminals
"It's the biggest, most important realisation of the Common European Foreign and Security policy. It has to succeed because, upon this, the whole of the rest of the policy will be based.
"We've got to show we have the capacity to do hard defence, that we can provide the troops, the command and the decision making process to cope with the security situation. The future depends on success here," says Lord Ashdown.
The EU force (Eufor) will have the same number of troops as SFor, around 7,000. Eighty per cent of the troops who are currently in SFor will remain in Eufor.
According to the planners, the only thing that will change will be the shoulder and cap badges. The aim is for a "seamless" transition.
But Nato is not totally leaving Bosnia. A small headquarters will remain in Sarajevo under the current commander of SFor, US General Steven Schook.
"Our principal mission after 2 December will be to provide advice on defence reform, focus on the apprehension of indicted war criminals and counter-terrorism," said General Schook.
The Nato office will also have an intelligence capacity, which Eufor will be able to draw upon.
But to what extent will the two international military organisations complement each other and to what extent could they get in each other's way?
The testing ground will be immediate. In the nine years since the end of the war Nato's SFor has arrested 28 war crimes suspects but has failed to arrest the two most wanted, the former Bosnian Serb political leader, Radovan Karadzic and his military commander, Ratko Mladic.
According to Lord Ashdown, both Eufor and Nato will have responsibility for pursuing war criminals. He rejects suggestions this will confuse the matter and make it easier for suspects to evade justice. General Schook agrees.
"With the sharing of intelligence between both organisations, I think you'll get a synergy that will be even better than we have now."
Many people in Bosnia remain suspicious of the Europeans
But he admits the division of duties still has to be finalised with the UK General Leakey who will head Eufor.
"We're still working the details of that co-ordination," concedes General Schook with less than eight weeks to go before the changeover.
But there's another potential problem, at least in one part of Bosnia.
"The Europeans let us down during the Bosnian War. It was the Americans who eventually stopped the war, not Europe," says Senad Alispahic, 26, a student at Sarajevo University.
"Many people here remain suspicious of the Europeans," he says.
Many Muslims and Croats in Bosnia blame Europe for failing to intervene to stop the three and a half year Bosnian War which left more than 200,000 dead and two million homeless.
It was the Americans who eventually led the military action which brought the war to an end. It is the Americans who are seen as the guarantors of peace.
'Anyone but the Americans' is a popular sentiment among Serbs
This view is not shared in the Serb-controlled half of Bosnia, where the mainly-American bombing took place. Eufor's arrival is being viewed from ambivalence to an "anyone but the Americans" attitude.
The stakes are high for Eufor. A mission characterised by inefficiency and failure will put back plans for a single European military force.
But a successful mission will help erase the bad blood caused by their perceived indifference during the Bosnian war, and perhaps provide a foundation for future deployments in other trouble spots including neighbouring Kosovo.