Relations between Russia and the West are at a new low. But how should we describe the current situation?
There's a lot of loose talk about a new "Cold War" - a comparison of present-day tensions to the bitter ideological and military rivalry that existed between the Soviet Union and the West from the 1950s to the end of the 1980s.
But such comparisons may be misleading.
"The Cold War," says Michael Kofman, a senior research scientist at the CNA Corporation and a fellow at the Wilson Center's Kennan Institute, "was a competition resulting from a bipolar system, where two superpowers, both with economic and military advantages, were competing to shape international politics.
"Their universalist ideologies made this competition inevitable, as did the distribution of power at the time."
In contrast, he says, today's competition is not the result of a balance of power, or universalist ideology per se, but "conscious decisions made by leaders, the strategies they pursued and a series of definable disagreements in international politics". And these were not "destined or inevitable".
So, while Mr Kofman believes the stakes could prove significant for the United States, the scale and existential nature of the conflict is nothing like the Cold War, nor is Russia in any position to fundamentally alter either the balance of power or the structure of the current international systems. "In short," says Mr Kofman, "the causes and character of the conflict are different."
During the real Cold War there was an armed peace in Europe, while the real battles were fought out across the globe from Angola to Cuba and the Middle East. Today's battle lines are generally much closer to Russia's own borders - Georgia and Ukraine.
There is a very different balance of forces between Russia and the West. Russia also has very limited "soft power", lacking an attractive internationalist ideology to "sell" around the world.
If the Cold War was a battle for global dominance between two universalist ideologies - capitalism and communism - what then is today's competition between Russia and the West really about?
Mr Kofman says that, for Russia, "it is about its survival as a power in the international order, and also about holding on to the remnants of the Russian empire".
"Russian leaders," he says, "are desperate to avert the further fragmentation of Russian influence and territory. They see no way to do this without maintaining buffer states and imposing their will on neighbours to secure their borders."
For the United States, Mr Kofman says, this is a confusing conflict. "One aspect of it", he says, "is a classic tale of hubris and over-extension; that is, too much liberal ideology and not enough thinking about international politics.
"Without any powers to contest American influence for two decades, Washington rightfully took advantage to build what it wanted, but all expansion of influence and power must eventually come with increasing cost, and those costs are starting to multiply in spades."
'Enemy deprivation syndrome'
It is increasingly clear that Russia, and China too for that matter, have not underwritten, and do not subscribe to, the liberal underpinnings of the post-Cold War order. And there is no way for the West to impose its will on these powers. So, in this sense, "great power politics" are back.
But many commentators say the West too has some responsibility for the current situation and playing up the new Cold War idea may only make matters worse.
Lyle Goldstein, a research professor at the US Naval War College, says: "Many in the West seemed to have succumbed to 'enemy deprivation syndrome' after the Cold War. Many national security specialists seem to yearn for a more simple threat that is easily characterised."
Situations in Georgia and Ukraine "seemed to offer the requisite storyline for new Cold War", he says. "However, these situations are incredibly complicated. And those most familiar with the region understand that both situations are a result of the rapid collapse of the Soviet Union with related identity and border issues."
So, what kind of power is Russia today? Mr Kofman describes it as "a weak great power." He says it is "consistently underrated because it historically lags behind the West in technology, political and economic sophistication, but Moscow consistently punches above its economic weight in the international system".
Russia is not, he says, "a declining regional power; quite the contrary".
"Indeed, after a period of internal balancing, military reforms and modernisation, Russia is more than capable of holding ground in its historic backyard, projecting power to other adjacent regions, and, as can be seen. reaching out to exact punishment on distant adversaries via non-military means."
In Nato countries, there is much talk about spending more on defence and of gearing up again to fight what's called a "peer competitor". For that, read Russia.
Some extra defence spending may well be needed - Western allies were far too quick to seek a peace dividend in the wake of the Cold War. But just what kind of military threat does Russia pose to Nato?
Prof Goldstein says Russia's forces are substantially weaker in the aggregate than those of the US and Nato. However, he adds: "Russia has invested wisely in the last 15 years, so that it has preserved certain niche capabilities that give it some advantages."
For example, Nato does not have a real counter to the Russian Iskander tactical nuclear system, and this could pose dilemmas for Nato commanders regarding whether to capitulate or escalate. Russia also has impressive capabilities in artillery and electronic warfare.
'Wars of choice'
But its capacities in cyber- and information warfare are most apparent and pose some of the most pressing challenges. Again, the media and think tanks alike are awash with discussions of an apparently new phenomenon - so-called "hybrid warfare" - a melding and blurring of the boundaries between peace and war at which Russia is perceived to be the new master.
As Mr Kofman notes, "no great power is a monochromatic threat". "In truth," he says, "Russia is both a potent military power in its near-abroad, just as it has the proven ability to conduct political warfare, cyber-warfare, and readily contest the information domain."
But Mr Kofman dismisses the fixation with hybrid warfare, saying this is "just an unintelligible Western reaction, after decades of wars of choice against paltry adversaries, to confrontation with another power that is capable across the full spectrum of conflict".
Prof Goldstein, too, says the obsession with hybrid warfare is problematic. "The real danger," he says, "is miscalculation that could set off a hot war that escalates out of control in either Syria or, most dangerously, in Ukraine."
'Calling Nato's bluff'
The so-called "hybrid" war in Ukraine has been actually shown to be "real war with mostly conventional forces", Prof Goldstein says. Indeed, he argues persuasively that the reason the US and Nato did not contest the Crimea annexation had nothing to do with "hybrid war" and everything to do with the actual military balance and the fact that Crimea and eastern Ukraine were perceived to be a part of Russian "core interests". The Kremlin, he says, "simply called Nato's bluff".
Another problem is that the West may not be using the correct tools in its efforts to influence Russia's behaviour. Indeed, it may not be entirely clear as to what it actually wants from Russia.
"Most of the tools used thus far are about assurance of allies and solving problems in alliance politics," Mr Kofman says, "but there is no discernible theory for how to influence Russian behaviour."
"Diplomatic measures," he says, "are good at maintaining political unity, but nobody in leadership even knows what they want from Moscow. Just trying to get Russia to 'stop' or to retire from international politics, or to capitulate in Ukraine, is not serious thinking - to put it mildly."
Diplomatic expulsions send signals about unity and resolve, but they are unlikely to change minds in Moscow. Most of the experts I speak to say that it is only economic leverage that will compel Russia to weigh up the true cost of its actions.
But beyond that, policy towards Moscow needs to be thought through from the fundamentals, bearing in mind that the repercussions from the chaotic collapse of the Soviet Union are still very much playing out some three decades later.