Exercises between US troops with Poland, Estonia, Latvia, Lithuania, which began last April, will expand through the summer, said Col. Michael Foster, of the 173rd Airborne Brigade, based in Vincenza, Italy. The exercises are part of the US Army Europe-led land force assurance training mission, known as Operation Atlantic Resolve — now expanded into "north" and "south" components.

"So by the end of the summer, you could very well see an operation that stretches from the Baltics all the way down to the Black Sea," Foster said, speaking at the Center for Strategic and International Studies here on Monday. "As you connect countries, there is almost a line of US troops."

The 173rd this week will also be sending nearly a battalion's worth of soldiers to the Ukraine to train troops from its national guard, considered separate from Atlantic Resolve, Foster said, "but certainly tied into deterring Russian aggression."