CBS's David Martin: The Buildup of Russian Troops Along the Ukrainian Border is Large and Getting Larger

Russian troops on the move. In the past two weeks about 20,000 Russian troops complete with tanks and artillery have gathered along Ukraine’s eastern border

Defense Secretary Chuck Hagel was concerned enough about growing numbers of Russian troops to have an hour-long telephone conversation with Russian Minister of Defense Sergey Shoygu about Russian intentions.

The Russian Defense minister told Hagel that the troops were participating in 'land exercises' and there is no intention of crossing the border into Ukraine.

The troops are less than 100 miles from the Ukrainian border. David Martin reports on the buildup and the growing concern of a possible invasion