If the Ukraine crisis erupts into war--even intensified limited war in Eastern Ukraine with overt Russian intervention--the consequences will be severe and far-reaching.
Among possible courses of action: neutrality for Ukraine; an alternative European security arrangement; a long-term moratorium on NATO expansion; or some combination of the foregoing and other measures.
A non-comprehensive list includes: vastly greater loss of life due to armed conflict in Ukraine; destabilization of global peace and security, not least the always urgent pursuit of nuclear arms control and disarmament; and impairment of the will and capability for cooperation on climate protection, public health, and other vital matters.
The proximate cause of the crisis is Russia's menacing behavior, including deployment of troops and equipment near the border with eastern Ukraine and in Crimea and Belarus, and conducting a nuclear forces exercise in Belarus.
Especially in context and combined with Putin's at times bellicose rhetoric, these actions are unlawful threats under the fundamental UN Charter prohibition of the "threat or use of force against the territorial integrity or political independence of any state."
In the case of the exercise, it is also an unlawful threat because it is contrary to general international law to threaten the commission of an illegal act--here the use of nuclear weapons.
Longer-term causes of the crisis are the utterly reckless declaration, made in 2008, the last year of the second George W Bush term, that NATO membership is in principle open to Ukraine and Georgia; and more broadly the long history since the mid-1990s of US and NATO disregard of Russian security interests and proposals.
To take just one example, when the first GW Bush administration determined that the US would withdraw from the ABM Treaty, Russia proposed renegotiation of the treaty. The US answer was simple: No.
The United States then proceeded to establish missile defense facilities in Romania and Poland that Russia, with some reason, regarded as destabilizing.
The only rational path is diplomacy. At two Security Council meetings on Ukraine, on January 31 and February 17, this was the refrain of all Council members, including Russia.
Diplomacy is indeed mandated by the UN Charter, which requires member states to "settle their international disputes by peaceful means in such a manner that international peace and security, and justice, are not endangered."
As the Russian response to a US proposal conveyed, there is some common ground for negotiation on such matters as limits on military deployments and regional arms control, conventional and nuclear. Former US Ambassador to Ukraine Michael McFaul surveys possible topics in this recent Foreign Affairs article.
However, as Russia has been insisting, what is lacking above all is US interest in addressing Russia's categorical opposition to even the possibility of NATO membership for Ukraine. Instead, the United States has been mechanically saying that foreclosing that possibility is a "non-starter".
This displays a lack of the creativity and imagination that diplomats on occasion are quite capable of putting to good use. Among possible courses of action: neutrality for Ukraine; an alternative European security arrangement; a long-term moratorium on NATO expansion; or some combination of the foregoing and other measures.
Also, a resolution of the status of eastern Ukraine will have to be reached, with the people of that region having a voice in the outcome. Similarly, the status of Crimea will have to be addressed or the issue deferred.
The stakes are very high. Energetic, creative, and determined problem solving is imperative.