Russia masses troops near Ukrainian border

MOSCOW — President Vladimir V. Putin ordered a surprise exercise of ground and air forces on Ukraine’s doorstep Wednesday, intending to demonstrate his country’s military preparedness at a time of heightened tensions with Europe and the United States over the turmoil gripping Russia’s western neighbor. The Obama administration said any Russian military intervention in Ukraine would be a costly and “grave mistake.”

Russia’s military put tens of thousands of troops in western Russia on alert at 2 p.m. for an exercise scheduled to last until March 3. The minister of defense, Sergei K. Shoigu, also announced unspecified measures to tighten security at the headquarters of Russia’s Black Sea Fleet on Ukraine’s Crimea peninsula.

Read the rest here.