Diplomatically, the alliance has kept together well through months of crisis. But the price has been a lack of military effectiveness. The key European allies - Britain, France, Italy and Germany - have been sharply divided over the war.
Britain and to a lesser extent France have been keen to escalate the conflict, with Mr Blair pushing publicly for a ground war. Italy and Germany have been far less keen, withboth countries insisting that there could be no land invasion under any circumstances.
America has stayed in the middle, refusing London's pressure for ground operations and blocking moves from Berlin and Rome for a bombing pause.
Militarily, the need to keep the allies together imposed severe constraints. Target lists were pared down to accommodate alliance concerns; operations had to be agreed through cumbersome structures in Brussels and Mons.
The war makes clear that a European defence policy run by the EU is a far off. Had there been a ground invasion, it would almost certainly have been led by American troops, with the British and probably the French accompanying.
Though the Europeans were well-represented in the early stages of the war, this was not the case as the number of air strikes went up. The combined contributions of France and Britain paled in comparison with US efforts. The war will help America press its view that Europe must spend more on weapons, especially advanced technology. The Europeans will argue that they need to create their own defence structures around the European Union.
The US Air Force will claim a victory for air power, while its critics will say that the war in Kosovo showed precisely the limitations of aerial force.Reuse content