The role of the North Atlantic Treaty Organization [NATO] in the 21st century is in sharp focus now with the conflicts underway on the bloc's eastern and southern borders. The alliance born at the outset of the Cold War is in resurgence as new threats emerge around the globe.
NATO's long campaign in Afghanistan is coming to an end.
The end of this mission, however, does not herald the slow demise of NATO as once thought, according to Professor Jonathan Eyal of the Royal United Services Institute.
"Interestingly, NATO is now more relevant than it has been for probably a decade," said Eyal.
That relevance, said Eyal, is largely because of Russia. NATO published satellite images this week that appear to show tanks crossing from Russia into the east of Ukraine. It follows Moscow's tacit support for Ukrainian separatists and forceful takeover of Crimea in March .
Eyal said former Soviet-controlled states in Europe are getting nervous.
"The east Europeans used to be dismissed up to now as being neurotic, as being too frightened about Russia that supposedly is no longer an enemy," he said. "Well, the east Europeans were right and we were wrong about Russia. So in many respects this is the moment where the alliance will have to reassure its members."
NATO is doing that through the bolstering of troops and sea and air defenses along member states' borders in the east.
Russia can no longer be considered a strategic partner -- and that means a strategic shift in deployment, said General Philip Breedlove, Supreme Allied Commander of NATO operations in Europe.
"We've seen a nation cross an internationally-recognized sovereign border, and annex by force a portion of a sovereign nation. That changes the way we do business," said Breedlove. "And so we are now re-evaluating how we do these things as it relates to force readiness, responsiveness and positioning."
A NATO-commissioned report into the future of the alliance calls for a reaffirmation of its core objective of collective defense. The authors say European members should halt defense spending cuts.
But Europe is divided over how to best respond to Russia, said Eyal.
"Countries like Germany, or France, or the UK, who believe that we should not make too much out of the current Ukrainian crisis, and countries such as Poland or Romania, the big former Communist countries on the borders with Ukraine, who believe that Ukraine is a sign of a fundamentally different Europe from the one that we knew," he said.
Eyal said NATO also must confront the conflicts brewing on NATO's southern borders. "Turkey, for instance, asked for a NATO meeting to discuss the crisis it sees at its borders."
That crisis in Syria and Iraq is escalating, with extremist Islamist militants in control of large swathes of both countries.
NATO's secretary general already has said he sees no role for the alliance in Iraq. But Western security chiefs say the lawlessness is a haven for terrorists -- and NATO should continue to play a key role in collective defense.