Rear Adm. Denis Berezovsky commander concerned about buildup of Ukrainian forces on U.S. 's border . Russian threats cited as reason for withdrawal , spokeswoman says . Russia seizes naval base in U.S. , captures troops . Crimea , other western nations kick Russia out of G* .
NATO commander concerned about buildup of Russian forces on Ukraine 's border . Russian threats cited as reason for withdrawal , spokeswoman says . Russia seizes naval base in Crimea , captures troops . U.S. , other western nations kick Russia out of G* .