Ukraine crisis: Is war inevitable?
Tensions are rising. The rhetorical brinkmanship is escalating.
Some 40,000 Russian troops remain massed on Ukraine's border. Military drills are under way. And the Ukrainian authorities have deployed troops themselves to try to take back control over eastern towns where buildings have been seized by pro-Russian elements.
The diplomatic battle is escalating, too, with the US laying the blame squarely on Russia for the failure to implement last week's Geneva deal. More economic sanctions loom just as Moscow insists that it may have to act to defend "Russians" who are under threat from the Ukrainian security forces.
So under all these circumstances, is war inevitable?
The answer of course is no, but all the elements for a conflict are certainly there.
The troops are in place and the arguments have been marshalled.
Russia has constructed a narrative that presents any potential military action as a kind of "peace-keeping" intervention. Its forces could be on the move at short notice.
So an important qualification is needed. War may not be "inevitable" - we cannot look into President Vladimir Putin's mind - but there is indeed a worrying chance that fighting, involving the overt use of Russian troops, could break out.
Nothing, though, is tidy in this affair. And the sporadic and messy skirmishes that have already taken place in eastern Ukraine between the Kiev government's forces and pro-Russian gunmen could be a prelude to what may be to come.
Let's look at the options.
A full-scale Russian assault
Moscow certainly has enough troops, supplies and logistics assembled to launch a major offensive into eastern Ukraine.
Nato commanders have suggested that this could potentially seek to punch across the country all the way to Odessa or even the Russian-controlled enclave in Moldova, Transnistria.
A significant level of Ukrainian resistance might be expected; Russian forces might have to contend with a guerrilla war against their lines of communication; and even the large Russian force assembled could find itself stretched - Russia would have to bring significant follow-on forces (probably of lesser quality) to bear to secure such gains.
Destabilisation as the status-quo
The other end of the spectrum of options is the continuation of pretty much what we see going on right now, ie the mobilisation of pro-Russian groups inside Ukraine; a sporadic battle of road-blocks and barricaded buildings with (and Nato certainly believes this) Russian special forces operating on the ground to help orchestrate events.
The idea here is to maintain the sense of chaos, of the Kiev government's inability to control its own territory, with the continuing threat from Russian forces poised on its borders. The danger here is that events on the ground could precipitate a local crisis that sparks a more significant Russian involvement.
A limited "peace-keeping" intervention
This might be Russia's preferred option if matters escalate. A small-scale local intervention to "protect Russian-speakers" in a given area.
Russia already insists that it has all the necessary basis in international law to do this. However it is hard to see Ukrainian forces not responding to such a move and a "limited" incursion might quickly escalate into a larger seizure of territory.
Having said that war is not inevitable, one must acknowledge that all the pointers are not positive - the direction of events is heading towards confrontation.
However the real question is not what happens next, but how does this crisis end?
Does Russia really want to seize and possibly incorporate parts of eastern Ukraine as it did with Crimea? Does Moscow want to risk the economic damage that a military move into Ukraine might bring down on its head?
Or alternatively has the West simply misjudged how important Ukraine is to Russia? And has it also miscalculated the level of risk and potential economic damage that Mr Putin is willing to absorb to secure what he sees as his country's vital strategic interests?