Several commentators including Mearsheimer, Pillar, Kirchick, and Goldgeier have weighed in already, with the first pair implicating NATO expansion in the current crisis and the second pair pushing back. I won't adjudicate between them except to say that I think Goldgeier's article sidesteps the question. He seems to argue that, because expansion helped eastern European states democratize and avoid conflict with each other, expansion did not increase Russian insecurity (even if it provided other benefits, expansion may still have made Moscow nervous). He also asks how fearful the Baltics and Poland would be today had they not joined the alliance, which ignores the counterfactual at the core of the debate: what would Russian behavior have looked like had the Baltics and Poland stayed out?
I was left with two main questions after reading these and other contributions. Did NATO really break a "no eastward expansion" promise made to Gorbachev as is often claimed? And was expansion simply a calculated response to Russian aggression toward its neighbors during the '90s? I looked back, briefly, at the history of NATO enlargement to try to find the answers.
A (repeatedly) broken promise?
Critics allege that enlargement violated a pledge to Moscow that NATO would not expand. An understanding was supposedly reached during negotiations over German reunification in 1990. Confirmation of a broken promise would strengthen the critics' case, since it provides another reason aside from territorial encroachment for Russian leaders to be suspicious of the alliance's eastward push. Gorbachev insists a pledge was made, yet some American and West German officials deny it.
Unfortunately, there is no consensus even among those who sort through the same evidence (compare this report with this article). If you were trying to figure out whether to code this case as a "promise" or not, it would not be easy. One source of confusion is whether phrases like "forces will not extend to the East" refer only to East Germany or to eastern Europe in general. (It's likely that the discussions were about East Germany specifically since expansion farther eastward was inconceivable at the time, but this just helps critics argue that NATO expansion has been extreme compared to the informal 1990 negotiating positions).
There's also confusion over who exactly spoke for the West. There were separate conversations about a possible pledge between Moscow and American officials on the one hand, and between Moscow and West German officials on the other. Finally, it's unclear whether verbal agreements about the pledge were in themselves promises or whether the verbal agreements were simply acknowledgements that the pledge would need to be included as part of a later, more formal agreement (the pledge was not formalized). The evidence in favor of a promise may be weak, but Lavrov and other Russian FMs have claimed Western duplicity anyway.
A response to Russian aggression?
Kirchick argues that the Russians brought NATO expansion on themselves through aggressive policies such as energy coercion aimed at neighboring countries. It's a short step from there to the contention that the alliance simply expanded as a reaction to Moscow's behavior. A responsive expansion would undermine the "blame NATO" argument.
Such a calculated approach to expansion was proposed by at least one early observer. In an unpublished paper from 1994 that still holds up, MIT's Barry Posen suggested the following (pp. 13-14):
The Partnership for Peace can be viewed as "NATO's Waiting Room." The tacit bargain with Russia is that many central European states remain in that waiting room so long as Russia remains a good neighbor. If and as Russia begins to try to expand its power, the din in the waiting room will become disturbingly loud. The elements are in place for the rapid extension of NATO to Poland, Hungary, the Czech Republic, and Slovakia, even if a threatened Ukraine is tossed to the wolves. Russia can, by its own acts, bring NATO to its doorstep. Stephen Oxman, Assistant Secretary of State for European and Canadian Affairs virtually stated this rationale... If, as some now argue, NATO expands eastward more or less as a matter of course, this useful sanction will have been lost.
It does not seem so. Instead, it seems that U.S. policy was driven by the belief that expansion would keep the alliance relevant, help to deal with new non-traditional threats, and help to consolidate democracy in eastern Europe. If expansion had been a calculated response to Russian behavior, we would expect this reasoning to be mentioned by leaders looking to justify the decision to skeptical outsiders.
But in September 1997, the Clinton administration responded to a letter from 19 Senators trying to understand the logic of expansion without mentioning any such justification. On the contrary, the administration argued, "The alliance must be prepared for other contingencies, including the possibility that Russia could abandon democracy and return to the threatening behavior of the Soviet period, although we see such a turn as unlikely" (emphasis mine). It is thus difficult to believe that NATO expansion was driven by Russian aggressiveness in the years just before the decision to expand. One wonders how different current events would be had the U.S. followed a strategy closer to what Posen, Oxman, and some others had envisioned two decades ago.