When the North Atlantic Treaty Organization (NATO) was created in 1949, the alliance was based on a system of "collective defense" which meant its member states agreed to mutually defend each other in response to an attack by any external party.

For most of the last half of the 20th century, the most likely external party was the Soviet Union. Not long after the signing of the treaty which brought NATO into being, the Cold War intensified and pitched NATO members into a standoff with the Warsaw Pact signatories which lasted over 40 years. Until the collapse of the Soviet Union in 1991, NATO's primary goal was to contain the threat that was thought to originate from behind its eastern borders.

Since the removal of the Soviet threat, NATO's goal in Europe has changed from defending its eastern borders to pushing those boundaries as far east as possible. In 2004, the alliance executed the biggest expansion in its history, to include seven new members: Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia -- all formerly part of the Soviet Union or the Warsaw Pact.

The alliance's expansion looks unlikely to stop there. A further five nations have been short-listed for NATO accession this year. While the membership of Albania, Croatia and Macedonia would mark a concerted effort by NATO to shore up the shaky Balkan region and consolidate its role there, a potential eastward push into Ukraine and, further still, Georgia has raised questions about NATO's current motives and approach to its former Cold War adversary, Russia.

NATO sells expansion as a means to stability

The leaders of NATO: Bringing stability or asserting regional dominance?

The official line from NATO is that membership in the alliance brings with it stability and security. The states being considered for accession have all recently experienced some form of political upheaval and instability.

"The Balkan region has been jolted anew by Kosovo's recent secession from Serbia," Charles Kupchan, a senior fellow for Europe Studies at the Council on Foreign Relations, in Washington, told DW-WORLD.DE. "NATO membership for Albania, Croatia, and Macedonia can help stabilize the region amid this new source of uncertainty. As in previous rounds of enlargement, preparation for membership encourages states to improve democratic governance and civilian control of the military."

But Dan Plesch, director of the Center for International Studies and Diplomacy, in London, and an author on global security issues, believes there is more to NATO's plans than the official explanation implies.

"The public explanation ignores Russia," Plesch said. "While NATO itself, and especially its European members, have no agenda to assert regional dominance around Russia, this cannot be said for some in the United States. For some in the US, NATO is just a vehicle and another opportunity to extend its hard power globally. Regional dominance is explicitly the agenda in Washington."

The proposed expansion of NATO's strategic defense forces further into former Soviet territory has angered Russia. Despite attempted conciliation during a recent bilateral summit with US President George W. Bush, outgoing Russian Premier Vladimir Putin still believes NATO expansion into Ukraine and Georgia would be a direct threat to Russia.

Putin reiterated his position to expansion in Bucharest

"The appearance of a powerful military bloc on our borders will be taken by Russia as a direct threat to the security of our country," Putin said at the NATO summit in Bucharest earlier this month. He also challenged NATO's argument that Russia would benefit from having stable, Western-backed democracies as neighbors. "The entry of Latvia into NATO has not changed a thing for those hundreds of thousands of people," Putin said. "NATO is not a democratizer."

Dan Plesch agrees that NATO's argument crumbles in the harsh light of reality. "The Latvian case just shows that NATO has a problem when it overextends itself. Continuing problems in far-flung outposts of NATO expose it as a meaningless alliance when these states go unsupported."

Russia: Playing the game or under threat?

Russia has reacted to the growing possibility of NATO expanding into Ukraine and Georgia by issuing bellicose warnings reminiscent of Soviet-era Cold War rhetoric. In February, Putin warned that Russia could take "retaliatory action" should Ukraine become a member of NATO, suggesting Moscow might aim its missiles at Kiev.

At the beginning of April, a senior Russian general reiterated Putin's message by saying that Russia would take "military and other" steps, should Ukraine and Georgia join NATO.

Some experts have speculated that President Putin's reactions are an assertion of Russian strength against a threat he knows to be manufactured. Others believe that Putin and his successor, Dmitry Medvedev, are genuinely concerned -- and have reason to be.

Ukraine's President Yushchenko has Bush's support

"NATO is not seeking to encircle Russia and assert regional dominance, but instead to extend stability, reassurance, and deterrence to new members," Charles Kupchan said. "In reality, however, NATO enlargement does bring with it greater Western influence and aligns the governments of new members with the Euro-Atlantic community. This realignment is one of the reasons that Russia is uncomfortable with enlargement; it diminishes Moscow's geopolitical sway. In that way NATO enlargement is in part a hedge against the potential return of Russian ambition."

There is growing concern that NATO expansion could spark a new arms race with Russia, leading to the Kremlin taking an even harder stance in the face of new social tensions brought on by spiraling defense costs.

"The worst case scenario would be a return to militarized rivalry between NATO and Russia, but this outcome is remote," said Kupchan. "What is more likely is increased Russian meddling in the Caucasus and less Russian cooperation on policies ranging from arms control and Iran, to missile defense and Kosovo."

NATO considering energy security in future missions

Even if NATO's expansion plans are not designed to curtail Russian ambitions and influence, the geographical significance of the countries hoping for membership holds other benefits for NATO's existing members.

No gas today: Russia cut Ukraine off in January 2005

NATO's increased emphasis on energy security for its members is recognized by some observers as a factor in its eastward expansion. Having been slower than Russia to seize on the impact of energy supplies on national security, it cannot have been overlooked by NATO that a presence in both Ukraine and Georgia would go some way to catching up.

Should both countries join the alliance, NATO would be in a prime position to exert influence over and protect oil supplies from the Caspian Sea through Georgia and offer support to Ukraine in any future disputes with Russia over gas.

Europeans delay membership

Russian anger over the planned expansion is also beginning to expose potentially damaging rifts within NATO itself. At the Bucharest summit, despite some last minute arm-twisting from President Bush, European leaders -- wary of alienating an increasingly assertive Russia -- denied coveted pre-membership status to Georgia and Ukraine, at least for the time being.

Merkel and Sarkozy led the opposition to expansion plans

Led by French President Nicolas Sarkozy and German Chancellor Angela Merkel, the Europeans claimed that such a move could destabilize an already volatile region on Russia's southern flank.

There are growing concerns that a split within NATO along European and US lines could lead to a breakdown in relations similar to that experienced over the invasion of Iraq in 2003. Others believe that remaining silent could be equally as damaging.

"France and Germany should take a stand," said Dan Plesch. "Russia is far more of a traditional European state than Turkey, and yet, it is Turkey not Russia that is now regarded as European. This goes against history and is a dangerous path. In this respect, Poland and the other former communist countries of central and eastern Europe are playing a dangerous game aligning with the US against Russia."

All these issues could be described as moot points seeing as it appears unlikely Ukraine and Georgia will become NATO members anytime soon, even with Ukraine's "membership action plan" due for reconsideration in December.

However, the tensions between all those with an interest in the expansion -- which will no doubt simmer and possibly increase between now and the resolution of the situation -- may be as defining as the final accession itself.