In Kosovo, Nato defeated Slobodan Milosevic in a war that displayed both its strengths and its weaknesses. We saw the might and the technological prowess that prevented a single Allied casualty, yet we also saw the unwieldiness inherent in forging a strategy on which 19 countries had to agree. Above all, however, the war laid bare the shameful reliance of the biggest European powers on American hardware to win a localised conflict in their own backyard. Kosovo merely underlined the obvious: that the EU was an economic giant, but a foreign policy and military dwarf.
Mr Robertson's in-tray will be bulging when he moves from the Ministry of Defence to Brussels in the autumn; he must oversee Nato's continuing operations in Kosovo and work to improve relations with Russia - even if that means a pause in the eastward expansion of the alliance, in particular into the Baltic states. But his biggest challenge will be to complete the shift in Nato's mentality from the Cold War to the 21st century, not least by fostering the development of a genuine European defence capability that does not harm transatlantic solidarity.
With the Government's widely praised strategic defence review, Mr Robertson has begun the reshaping of Britain's armed forces for the likely conflicts of the future, stressing rapid reaction and the ability to deploy power and impose peace in, perhaps, distant conflicts. This pattern will perforce be followed by Nato, and by Europe itself as it builds upon last December's Anglo-French agreement in St Malo to strengthen its defence "pillar". The task now will be to achieve this without arousing suspicion in Washington that a stronger Europe means a stronger rival, rather than a stronger partner.
The prospects for meshing Europe's evolving defence policy into Nato improved earlier this summer when the outgoing Secretary General, Javier Solana, was named the EU's first foreign and defence policy co-ordinator, under the 1997 Treaty of Amsterdam. With the appointment of Mr Robertson to succeed him, a man who is both a confirmed European and a senior Cabinet minister from America's most faithful and important military ally - and highly regarded in Washington, to boot - those prospects have brightened further.