By Suzanne Kelly
Special to CNN Interactive

BERLIN (CNN) -- The signs of turning 50 seem universal. It's often a time to re-evaluate goals, examine the past and plan once again for the future. And as the North Atlantic Treaty Organization turns 50, it is no different.

Although it is most likely not prone to buying a new red sports car in an attempt to reclaim it's youth, NATO is faced with the realization that as the world has changed around it, it too must adapt.

'The essence of security'

NATO is a baby of World War II. After enduring the aggression of Adolf Hitler, Western countries formed NATO as a means to protect themselves from the aggressive expansionist policy of the postwar Soviet Union.

Belgium, France, Luxembourg, the Netherlands and the United Kingdom joined together mainly to create a common system for defense. A year later, in April 1949, the United States and Canada agreed to join them -- along with Denmark, Norway, Portugal, Italy and Iceland -- in forming the North Atlantic alliance.

As NATO grew older, it also grew larger. Greece and Turkey joined the alliance in 1952, followed by West Germany in 1955, Spain in 1982, and in 1999, Poland, Hungary and the Czech Republic.

Christian Schwarz-Schilling, an international mediator for the Federation of Bosnia-Herzegovina, says NATO may be getting older, but it certainly hasn't outgrown its usefulness.

"It is still the essence of security in Europe," he says. "Without NATO, there is no security in Europe."

NATO surveillance video of Yugoslav targets being hit in late March 1999

Schwarz-Schilling says that although NATO may still be sound and able to initiate physical power, it is the mental support that is crucial to keeping the alliance fit.

"NATO does a job, but the politicians must have a firm will -- then NATO is efficient," he says. "They must form a close structure with the European Union to stabilize the continent, especially Eastern Europe."

New partners, new role

NATO military action in Yugoslavia has tested that resolve. It not only has been an opportunity for NATO to demonstrate its new and changing role in Europe, but it has also provided the opportunity for NATO to flex a little muscle. Politicians say that in a changing political environment, NATO's purpose remains unchanged: to defend the security and democratic values of its members.

A Tomahawk cruise missile is fired from the USS Philippine Sea in the Adriatic during 1999 NATO strikes against Yugoslavia

U.S. President Bill Clinton recently reminded U.S. troops bound for the Balkans that both world wars began in Europe, and that securing peace in the Balkans is essential to maintaining a secure Europe.

"Over the last five years we have been building a new NATO that is better equipped to deal with different challenges --with new missions, new members, and new partners across Europe, including Russia and Ukraine," Clinton said.

"Yesterday's NATO guarded our borders against military aggression. Tomorrow's alliance must continue to safeguard our shared security while contending with new threats that recognize no borders -- the spread of weapons of mass destruction, ethnic violence, and regional conflict," the president said.

The Russia question

As highlighted by the recent NATO action against Yugoslavia, the relationship between NATO and Russia continues to be a sensitive one. Russia has expressed concerns that NATO's eastward expansion could produce new dividing lines in Europe.

But with the end of the Cold War, why is Russia still kept at an arm's length from NATO?

Michael Kreile, professor of international politics at Humboldt University in the former East Berlin, says Russia is kept at a distance because NATO was created to protect Western interests from Soviet aggression.

Extending NATO membership to Russia "would change NATO in a very crucial way," Kreile says.

Russian President Boris Yeltsin has repeatedly denounced the NATO attacks against Yugoslavia

In effect, it would change NATO's original charter -- and cast the alliance's role into doubt once again. The question then would become, who is NATO protecting itself from? Western allies still see a political need for a "balance of power" that can only be kept intact if Russia remains outside the alliance, Kriele says.

Russia is currently included in NATO's "Partnership for Peace" program, created to give other countries the opportunity to participate in NATO actions without holding NATO membership. Kreile says it is critical to keep it that way.

"It is quite clear that NATO cannot act alone and in disregard of Russian interests, but including Russia as a part of NATO is simply not a viable option at this point."

Facing criticism

And it is no secret that Russia isn't happy with NATO's military action in the Balkans. Russia's leaders have stopped just short of making military threats of their own against NATO member countries in an attempt to stop the action, but some analysts say that Russia no longer has the might to challenge NATO, economically or politically.

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But Russia isn't alone in its criticism of the Yugoslavia operation. Many Western European newspapers also have voiced doubts about the NATO action. The day after the initial airstrike order was given, the International Herald Tribune wrote in a front-page news analysis:

"By taking the fateful step to authorize the bombing of Yugoslavia, the Western allies enter uncharted territory. Unlike the airstrikes against Bosnian Serbs that led to the Dayton peace agreement, there are no assurances that raids will persuade President Slobodan Milosevic to call off the latest offensive against ethnic Albanians in Kosovo."

Such criticism is prompting debate across Europe and in the United States and Canada over the role and focus of NATO as it turns 50.

Take a number

One thing is certain: As NATO gets older, it is likely to continue getting bigger, with Slovenia, Slovakia, Romania, Latvia, Lithuania, Bulgaria and Estonia waiting in line to join. Schwarz-Schilling says that indeed, it is these former Soviet satellites which can help NATO accomplish its mission in the future.

"The future planning for the next 10 years must be not only nation by nation, but for the whole region, especially for the Balkans," he says.

"The U.S. and the European members must tighten their leadership to integrate the climate for peace and stability and building up democracy and the economy in the Balkans," Schwarz-Schilling says. By inviting the former Soviet satellites into NATO, the alliance could hope to avert further instability in region.

So at an age when many people would be planning to slow their pace, NATO is beefing up -- and adjusting to its new role in the post-Cold war era.