The role of NATO— the trans-Atlantic military alliance founded in 1949 specifically to counter the Soviet Empire in Europe — has been an evolving discussion since the breakup of the USSR in 1991. 

Back then, many foreign policy experts were urging triumphant Western leaders to establish a new security framework to redefine relations with Russia, which inherited the ruins of the Soviet Union. 

The West "held all the cards in 1990-1991," Dan Plesch, a professor of diplomacy at the SOAS University of London, told DW. "The Soviet Union managed a [relatively] peaceful end to empire, which is almost unprecedented and for which they got no credit," he said.

The demise of the USSR led to a flurry of high-level meetings and negotiations between American and Soviet — later Russian — officials, but "we never made a serious effort to bring the Russians in," according to Plesch.

A hammer without a nail 

Amid intense political and economic instability in Russia during the 1990s, opposing the Western alliance was one of the few issues that united the country's fractious political spectrum, according to declassified documents maintained by the National Security Archive at George Washington University in Washington, D.C. 

"We believe that the eastward expansion of NATO is a mistake and a serious one at that," Boris Yeltsin, Russia's first post-Soviet president, told reporters at a 1997 news conference with US President Bill Clinton in Helsinki, where the two signed a statement on arms control. 

Indeed, documents show a pattern of promises US negotiators made to their Russian counterparts as well as internal policy discussions opposing NATO expansion to Eastern Europe. 

"In the current environment, it is not in the best interest of NATO or the US that [Eastern European] states be granted full NATO membership and its security guarantees," according to a State Department memorandum in 1990, while those states were still emerging from Soviet control as the Warsaw Pact disintegrated. "[We] do not, in any case, wish to organize an anti-Soviet coalition whose frontier is the Soviet border. Such a coalition would be perceived very negatively by the Soviets." 

Post-USSR order: Changing security policy 

None of these discussions ever became official policy, and none of the alleged pledges ever made it into a legally binding document with Russia. Moreover, they took place in a specific contemporary historical context: The Berlin Wall had just fallen in 1989. 

Especially the Baltic Sea states of Lithuania, Latvia, and Estonia — which were part of the Soviet Union from the 1940s to 1991 — saw an increased drive for political self-determination and a reorientation of the region's security structure.  

The three states pointed to the UN Declaration on the Inadmissibility of Intervention and Interference in the Internal Affairs of States, which refers to "political independence both internally and externally." 

NATO's open-door policy with Russia 

After the dissolution of the Soviet Union the Eastern European military alliance, the Warsaw Pact, disbanded in 1991. US president Bill Clinton pursued Partnership for Peace, which Russia joined in 1994. However, there was disagreement over whether that was an alternative to NATO membership or a pathway to it. 

In 1997 NATO and Russia signed the "Founding Act" on mutual relations, cooperation, and security, and the NATO-Russia Council was founded in 2002, both of which were intended to boost cooperation. Moscow received access and a permanent presence at NATO headquarters in Brussels. But this exchange has been largely halted since Russia's attack on Ukraine in 2014. 

All the while, NATO maintained an "open door" policy on membership and stood by all countries' right to choose their alliances. From the Western perspective, keeping NATO to its Cold War borders was only valid so long as Soviet forces remained in Eastern Europe.

In the "Two plus Four" negotiations for a reunited Germany in 1990, the two German states and the four World War II allies — the US, Britain, France, and the Soviet Union — agreed that no NATO soldiers may be stationed on the territory of the former East German communist GDR. To this day, only the German Bundeswehr operates here.  

Russia's sensitivities over NATO's possible eastward expansion were well known. "No matter how nuanced, if NATO adopts a policy which envisions expansion into Central and Eastern Europe without holding the door open to Russia, it would be universally interpreted in Moscow as directed against Russia," US diplomat James Collins wrote in a State Department cable in 1993. 

But since 1990, NATO has gone through five rounds of enlargement to include former parts of the Soviet Union and several former Warsaw Pact states. 

In 2010, NATO's strategic concept, which governs alliance policy, says "NATO poses no threat to Russia" and calls for a "true strategic partnership" between the two sides. The document came out two years after Russia's military intervention in Georgia but before its first attack on Ukraine. It is based on many of the post-Cold War arrangements that Putin now appears to want to abandon.

In 2008 NATO floated the possibility of Georgia joining and intensified cooperation with Ukraine in 2014. At the same time, many of the Cold War fail-safes — such as arms control verification and lines of communication — have fallen away. 

Misjudgment of Kremlin aims

NATO carried out an aerial bombing campaign against Serbia in 1999 during the Kosovo war. Serbia was a Russian ally. Vladimir Putin was elected president not long thereafter.

He still cites the bombing as proof of NATO aggression — also in the context of the current crisis.

The issue has taken a central role as he has ordered his armed forces towards Ukraine's borders, most recently sending some of them into breakaway regions that Russia supports. 

"If Ukraine were to join NATO, it would serve as a direct threat to the security of Russia," Putin said in televised remarks on Monday, during which he described Ukraine as a "springboard" for a NATO strike against Russia. 

NATO has dismissed Putin's sense of encirclement, given Russia's massive size that extends to the Pacific Ocean. However, the vast majority of the Russian population lives on the country's European side.

JD Bindenagel, a former deputy US ambassador to Germany, told DW that he believes NATO's mistake was not so much the actual enlargement, but with not taking seriously the Russian view that it had been betrayed. 

"We never engaged with it; we thought this was a ridiculous narrative. And so we would say, 'no that didn't happen,'" he said. 

Frank Hofmann contributed to this report.

Edited by: Rina Goldenberg

While you're here: Every Tuesday, DW editors round up what is happening in German politics and society.You can sign up here for the weekly email newsletter Berlin Briefing.