The defence-capabilities gap that divides the United States from its European allies is real, and it matters. The gap can most usefully be viewed as the aggregate of multiple gaps relating to the organisation and conduct of large-scale expeditionary operations. Transatlantic disparities in the ability to mount such operations became painfully obvious during NATO's Kosovo intervention in March-June 1999, and spurred commitments on both sides of the Atlantic to narrow the gap. However, a close examination of the European Union's post-Kosovo efforts to develop an autonomous military capability reveals serious obstacles to improving European forces. Chief among them is a deep reluctance to increase defence spending, in view of the low level of threat perceptions in NATO Europe and high social priorities in Europe.