There was a powerful symbolism in the fact that they started the Kosovo bombing at the Berlin summit in March and appear to have come close to ending it in Cologne. Kosovo is not Bosnia. The EU is now centre-stage, no longer the junior partner to Uncle Sam.
The seriousness of the leaders' purpose in establishing an autonomous European military capability was also emphasised by the appointment of the Secretary-General of NATO, Mr Javier Solana, to head the EU's new foreign and security policy unit and by the agreement to asset-strip the Western European Union (WEU), incorporating chunks into the Union.
For the Germans, the announcement of a Kosovo deal came as a blessing, elevating a somewhat lacklustre summit to a new status. The agenda had otherwise been dominated by internal housekeeping: jobs for the boys; the setting of dates for a new intergovernmental conference and an agenda for the Helsinki summit; the rebranding of the EU's jobs strategy as an "employment pact".
Even the defence declaration, given a new significance by the circumstances, was the diplomatic equivalent of staffing an office whose opening had been decided in the Amsterdam Treaty,
It was a slick production, though, which did the Germans credit. However, they did not have it all their own way: Bonn's hope to see the merger of the WEU and EU was emasculated; their early ambitions for explicit growth targets in the employment pact went the way of its architect, Mr Oskar Lafontaine; and the Chancellor, Mr Gerhard Schroder, had to admit last night to having failed to persuade Greece and Spain to unblock two major decisions.
Germany had hoped to send a gift to Turkey in a clear statement that it would soon be joining the ranks of official candidates for EU membership. Athens was having none of it, and Mr Schroder, at his final press conference, could only apologise, warning strongly of "the need to keep the door open to Turkey".
Spain, meanwhile, refused to lift its objections to the draft European company statute, now 29 years in the making.
However, Mr Schroder did have his way in bulldozing through the appointment of a deputy to Mr Solana in the French nominee, Mr Pierre de Boissieu, its ambassador to the EU.
"If there had been a vote it might have been different," the Taoiseach, Mr Ahern, admitted wryly.
The Danes, who had a strong candidate in their envoy, Mr Poul Crisstoferson, made no bones about what they saw as a carve-up by the big boys of the plum jobs. The Germans and British also have their eyes on the vacancy which will arise in NATO.
From an Irish perspective, the summit was a success, not least in raising the prospect that the Yugoslav match might yet be played. The defence debate had a number of dangers. Somehow the WEU's Article 5 commitment to mutual defence guarantees had to be sidelined, not a major problem as the British, among others, regard it as inappropriate to the EU.
Just as significantly, Dublin was determined to ensure that any political/military structures which emerged in the EU would not involve two classes of membership, one for NATO members, another for neutrals. That will not be the case, and so we can expect that when some of the planning functions come over from the WEU the two Irish Army officers currently seconded to it will also move.
The Swedes and Austrians were also selling heavily to their journalists, although not entirely plausibly, the declaration's reference to the new EU capacity being used "in accordance with the principles of the UN Charter". That meant, they said, that no military action could be taken without a UN Security Council mandate.
Was that the case? Mr Schroder was asked "Yes," was all he would say.
"That's the aspiration," said a NATO diplomat.
The Minister for Finance, Mr McCreevy, will also have been glad to see the Spanish Prime Minister, Mr Jose Maria Aznar, demolish single-handed a proposed declaration reference to the need for a tax on energy products to which Ireland is strongly opposed. The text was also amended to make it clear the EU was not opposed to tax competition but to its "harmful" variant.
There was also good news for the applicant states of central and eastern Europe. A final declaration strongly hinted that it will be possible to open full accession talks with Malta, Bulgaria, Romania, Lithuania, Latvia and Slovakia. The summit also backed a stability pact for south-eastern Europe based on financial support.