Of course, it's still too early to say definitively what happened but this is a blog, not a news article or a government report, so I have the space to vent and express what I think rather than what I know. So, here goes.
Although I wish it were otherwise, I feel the overwhelming odds are that MH17 was shot down by a Buk-M1 surface-to-air missile fired by the rebels (but supplied by the Russians):
1. The rebels, notably generalissimo Strelkov actually claimed to have shot down a government An-26 in the general area of the MH17's demise. The social media claims in question have been retrospectively deleted, but in this age nothing is truly lost.
2. The rebels have shot down other government planes and indeed there is strategic merit to their denying their airspace to Kiev's forces, given that air power is one of the government's real advantages. If they thought the MH17 was a government plane, then this might have seemed a great opportunity.
3. MH17 was flying too high for the man portable and light vehicle-mounted SAMs the rebels have openly deployed, but recently they admitted-and again these claims seem to have been retracted-to having at least one Buk-M1 SAM system, a tactical battlefield system that has the range to claw a civilian airliner out of the sky, and the warhead to do it with one hit.
4. The Buk is a radar-guided missile, so it could quite possibly have been launched without any eyeballing of the target. Furthermore, while the rebels may have the Buk's radar targeting system, they lack the extensive radar network and, above all, the skilled sensor operators who might have been able to tell a passenger airliner from a government troop plane.
5. The pattern of wreckage, the state of the corpses, suggests a catastrophic in-air impact and then rapid descent, not a crash from engine or system failure. Again, this speaks to a missile attack, and there do not seem to have been Russian or Ukrainian fighter jets in the air near there. So, again we're back to a SAM.
Yes, I am excluding the more outré conspiracy theories, that MH17 was destroyed by government forces to demonize the rebels and likewise that it was shot down by an S-300 from Russia. This was, in my opinion, a tragic and murderous blunder rather than an intentional atrocity. This in no way excuses the attack-human lives are human lives, whether Ukrainian airmen or multinational civilians-but helps explain what's going on.
Either way, I suspect that when the histories are written, this will be deemed the day the insurgency lost. Or at least began to lose. Especially given the presence of Americans and other Westerners on MH17, the Kremlin will, for all its immediate and instinctive bluster and spin, have to definitively and overtly withdraw from arming and protecting the rebels. This is especially considering the presumption that Moscow supplied the missiles in the first place. A single Russian report alleged that the rebels had captured a Buk from Ukrainian government stocks, but this was almost certainly preemptive disinformation as there is nothing else external to the rebels' own propaganda to support this claim. Besides which, while it is not that difficult to find crew for artillery, even tanks, the Buk does require well-trained crews, and ones trained relatively recently.
Meanwhile, Kiev's determination to defeat the rebels will not only be strengthened, it is likely to be blessed by the West. It's not inconceivable that we will not only see Western MREs (meals, ready to eat) and body armor being deployed, but Western lethal weapons, trainers and even special forces.
Without Moscow's support, the insurgency cannot last for that long. That is not to say that when it goes down, it will go down easy. If anything, the opposite is true as they may no longer have the option of finding sanctuary in Russia. Fighters with their backs to the wall are always dangerous.
Mark Galeotti is Professor of Global Affairs at New York University's Center for Global Affairs, where his focus is modern Russian history and security affairs and transnational and organized crime. He has published widely, with 13 authored and edited books to his name, and writes a personal blog at inmoscowsshadows.wordpress.com, where this post first appeared.