Just before U.S. Route 93 crosses over into Canada, it bisects Eureka, Montana, a ranching town that sees few visitors apart from the handful of hikers and fishermen who trek to the area each summer. On a mild day in June 2012, a caravan of vehicles with tinted windows sped a few miles past the town center and turned off onto a winding road leading up into the mountains. The cars reached a cluster of modest clapboard houses in a vast green pasture, and several Russian government officials climbed out. They wore dark suits and sunglasses that shielded their…