An heading overseas to Ukraine and the new dominos falling as Russian sympathizers gain more ground. ABC's Martha Raddatz in the region with American troops. Reporter: Tonight, pro-russian mobs taking... See More
An heading overseas to Ukraine and the new dominos falling as Russian sympathizers gain more ground. ABC's Martha Raddatz in the region with American troops. Reporter: Tonight, pro-russian mobs taking control. More government buildings. As Putin demands Ukraine to pull back its troops. One spot after another across eastern Ukraine falling. This as Ukraine's leader saying his forces are helpless, losing parts of the country. Fear spreading across the region. It's why hundreds of American troops have arrived here for joint training in Latvia where those fears of a Russian invasion are very real. You've seen what has occurred in Ukraine, crimea, and so to them it's a real threat. Reporter: With 50 pounds of gear, injury training, and live fire, the soldiers navigate a mile long course as rapidly as possible. This is called a stress shoot. Not only are they shooting, they are running to raise the heart rate. A grueling exercise for Americans and one that forges a bond between the allies. Okay? Yeah. Does having the U.S. Troops here send a message to clad mere Putin? I believe so. What's that message. Not to step in the nato countries. The question now is Putin listening?
This transcript has been automatically generated and may not be 100% accurate.