Updated

A high-ranking NATO official says Europe must change its thinking from the times when international borders were considered permanent because the "paradigm has clearly changed" following Russia's annexation of Crimea.

U.S. Air Force Gen. Philip Breedlove says NATO is responding to the new and evolving military situation in Europe by increasing military maneuvers in Poland, Romania, the Baltic region and the Black Sea.

In an appearance Tuesday in Lisbon, Breedlove reaffirmed NATO's commitment to collective defense, where an attack on one member is deemed an attack on all.

The Baltic nations of Estonia, Latvia and Lithuania are increasingly worried that Russia's annexation of Crimea could lead to destabilization in their region. All have significant Russian speaking minorities.