NATO Leaders Meet to Deal With Threats From Russia, South

British Prime Minister David Cameron grimaces sitting next to US President Barack Obama before the first working session of the North Atlantic Council at the NATO summit in Warsaw, Poland, Friday, July 8, 2016. Starting Friday, US President Barack Obama and leaders of the 27 other NATO countries will take decisions in Warsaw on how to deal with a resurgent Russia, violent extremist organizations like Islamic State, attacks in cyberspace and other menaces to allies' security during a summit described by many observers as NATO's most crucial meeting since the 1989 fall of the Berlin Wall.AP Photo/Markus Schreiber

WARSAW, Poland—Leaders of the NATO military alliance on Friday began a landmark summit that will order ambitious actions against a daunting array of dangers to the security of their nations and citizenry, including a rearmed and increasingly unfriendly Russia to Europe’s east and violent Islamic extremism to the south.

“As the challenges we face change and evolve, so does NATO,” alliance Secretary-General Jens Stoltenberg said as the summit opened. He said the decisions to be made by U.S. President Barack Obama and the 27 other heads of state and government will “shape NATO for years.”

The trans-Atlantic political and military alliance, founded in 1949, must adapt “so our people are safe, our countries are secure and our values are preserved,” said Stoltenberg.

Polish President Andrzej Duda, the summit’s official host, warned that Western democratic values are being undermined by a “notorious lack of respect for international law” as well as terrorism and new high-tech techniques of warfare, and said NATO needs a coherent strategy to combat those problems.

President Barack Obama shakes hands with Polish President Andrzej Duda after making statements following their meeting at PGE National Stadium in Warsaw, Poland, July 8, 2016. AP Photo/Susan Walsh