By Tom Balmforth MOSCOW (Reuters) – Russia launches the active phase of vast military exercises in Belarus on Thursday, a display of strength that shows how Moscow’s tightening grip on Minsk has given it enhanced capabilities in its standoff with the West over Ukraine. The joint Allied Resolve drills that NATO has described as Russia’s biggest deployment to ex-Soviet Belarus since the Cold War run until Feb. 20 and are part of a Russian troop buildup near Ukraine that has stirred fears of a looming invasion. Russia, which denies any invasion plans, has not disclosed how many troops will be inv…