The ongoing crisis in Ukraine is the final nail in the coffin of a Western strategy of "strategic ambiguity" with regards to the states of post-Soviet Eurasia--an approach that had already been seriously compromised in the wake of the 2008 clash between Russia and Georgia. For the last two decades, the corollary to giving Russia a "voice without a veto" in Euro-Atlantic security affairs has been to offer Russia's neighbors a "pledge without power"--to make promises which appear to convey binding security guarantees but without creating the mechanisms for their enforcement.

Strategic ambiguity was designed to square three very different circles. The first was how to reassure countries newly freed from the Soviet yoke that, as Russian power resurged, they would not find themselves under threat from Moscow. The unhappy experience of the three Baltic States--which enjoyed twenty years of independence between the two World Wars only to be incorporated into the Soviet Union--drove efforts to seek binding security guarantees from the Western powers. The second was how to avoid complicating U.S. (and European) relations with a Russia that might, under the right circumstances, become a true partner to and even member of the Euro-Atlantic world. The final and perhaps most decisive consideration was to avoid taking on burdensome new obligations or political costs.

The three subsequent post-Cold War expansions of NATO took place because of the belief that these three problems could be minimized; that the danger of great-power war in Europe had faded forever (and thus extension of membership and with it the binding security guarantees carried no real risk of being acted on); that Russia would not really object; and that expanding the alliance would be more or less cost-free. Taking in former members of the Warsaw Pact was one thing, but when it came to former Soviet republics, Russia raised the level of its objections. The Baltic states, in part because of their history, did make it into the alliance--but did so in part on the assumption that NATO would never have to take conventional military action to defend the new members--hence the lack, for many years, of real contingency plans to defend these states in the event of a Russian strike. Indeed, one might argue that if the Balts were coming up for membership now, in the light of Russia's moves towards rearmament and reconstituting its military capabilities, whether NATO would still be so sanguine about their application, or whether the alliance's members would find justifications for why membership would not be advisable.

Yet neither the Europeans nor the United States wanted to explicitly draw lines and state that beyond "here lie dragons." Thus, the importance of strategic ambiguity. The promiscuous usage of the term "partner"--to suggest a quasi-alliance relationship with a country without any formal treaty guarantees--has been particularly problematic. States like Ukraine, Georgia and Azerbaijan offered military forces in support of U.S.-led operations in Iraq and Afghanistan, believing in a transactional approach to international relations--that their willingness to put forces to fight and die alongside U.S. troops in the Greater Middle East created a reciprocal obligation of the United States to, in turn, guarantee their own security. The clear, bright shining line between an ally with a Senate-confirmed mutual defense treaty and concrete contingency planning for security and a "partner" who received U.S. security assistance funds and basked in presidential speeches and non-binding Congressional resolutions promising support was allowed to be blurred.

"Partners" could also have a double meaning. It could be deployed with pro-Western politicians in various post-Soviet countries as a virtual synonym for alliance. But U.S. diplomats in Moscow would try to soothe the concerns of the Kremlin by noting that even Russia and the United States were partners. Indeed, the explosion of the term to cover nearly every country of the globe has been to shear the term of any substantial meaning.

Contemplating the terminology of "partners" has been the growing tendency of the U.S. president--of whatever party--to rely more on executive agreements and informal "understandings", replacing formal treaties which require Senate confirmation. Part of this is due to growing domestic political dysfunction which has complicated executive-legislative relations. The problem, of course, as the late William Safire noted, is that what the president "giveth" he can also "taketh." He can decide to unilaterally reinterpret, modify, or even ignore what he has pledged or promised.

This brings us to the question of the legal standing of the 1994 Budapest Memorandum, in which the United States (along with the United Kingdom and Russia) pledge to guarantee the security and territorial integrity of Ukraine. This promise was an important incentive in getting Ukraine to give up its nuclear weapons. However, it is not akin to the treaty which created Belgium and which guaranteed its security--the stated reason for Britain to declare war on Germany in 1914 after the German army violated the Belgian frontier. It is, as the title suggests, a memorandum. It was never ratified by the Senate and it offers no security guarantees whatsoever to Ukraine. One can argue that there is an explicit moral commitment. But there is no binding legal commitment for U.S. intervention should Washington conclude that Ukraine has indeed, become a victim of aggression.

Vladimir Putin is testing what are the real "red lines" of the United States and Europe. It is not accidental that Putin got the Federation Council to give him a unanimous vote to deploy Russian military forces in Ukraine--a not so subtle rebuttal to a U.S. president whose rhetoric about action was not matched by Congressional authorization or public support. It also presents an unwelcome task for U.S. policymakers who must now begin to bring clarity to our deliberately ambiguous statements.

Nikolas K. Gvosdev, a contributing editor at The National Interest, is a professor of national-security studies at the U.S. Naval War College. He is also the co-author of the recently-published Russian Foreign Policy: Interests, Vectors and Sectors (CQ Press, 2013).

The views expressed are entirely his own.