U.S. Army paratroopers are arriving in Poland to begin a series of military exercises in four countries across Eastern Europe to bolster allies after Russia's annexation of Ukraine's Crimean peninsula last month.

The Pentagon press secretary, Rear Adm. John Kirby, said Tuesday that the exercises would last about a month, and initially involve about 600 troops.

An Army company of about 150 soldiers from the 173d Airborne Brigade Combat Team will start the exercises Wednesday. Additional Army companies will head to Estonia, Latvia, and Lithuania and are expected to arrive by Monday.

The exercises are part of an effort announced last week by Defense Secretary Chuck Hagel aimed at reassuring NATO allies of America's commitment to the region's defense.

"It's a very tangible representation of our commitment to our security obligations in Europe," Kirby said, "and the message is to the people of those countries and to the alliance that we do take it seriously. . . . And we encourage our NATO partners to likewise look for opportunities of their own to do this same kind of thing for one another." - APEndText