As Estonia's Defence Minister Hanno Pevkur prepared to fly to the NATO summit in Ankara this month, he revealed to local journalists that several hundred U.S. troops deployed to his Baltic nation in the winter had quietly been withdrawn – with no clear sign of when or whether they might return. At the Ankara gathering itself, delegates from the Baltic states and Poland proudly wore badges proclaiming themselves members of the "five percent club", the only nations in the NATO alliance to have already reached the spending target set at last year's meeting in The Hague – a status they...