Good evening to you on this tuesday night. And we begin with that faceoff between two of the worlds superpowers. Russia and the United States, in a chess game filled with tension, tonight. The eyes of the world, still right here. On one side, europe. On the other, driven by Vladimir Putin. And in the middle, ukraine, crimea, and an international tugofwar. Abcs Martha Raddatz is traveling with the secretary of state. And she is standing by. And abcs chief foreign correspondent, terry moran, is also on the story tonight. Starting us off with the latest on that crisis in ukraine. Reporter at belbek air base here this morning, ukrainian troops, unarmed, marched toward the russian guns. And as they marched, they sang their national anthem. [ singing ] confronting the russians who had seized control of their base, forward under the ukrainian flag they came. The russians yelled, then fired. Warning shots. But the first shots fired here. Negotiations and the ukrainians withdrew, heads held hig