NATO’s new rapid-reaction “spearhead” force, meant as a deterrent to Russian aggression, should be up and running with initial capabilities in less than a year, a top alliance official said Thursday. The creation of a 4,000 to 5,000 troop response force, which will be able to respond to a crisis in eastern Europe within two to three days, was a key decision taken by NATO leaders earlier this month in Wales. The force represents a calculation by NATO that Russian President Vladimir Putin won’t risk going head-to-head with the Western alliance. …