We are closer than we were a week ago to a military balance in eastern Ukraine that could allow for a ceasefire to take hold, assuming that a ceasefire is what Kyiv and Moscow want, but I do not believe we are there yet. The problem is that the current disposition of forces is not conducive to an end to the fighting. Ukrainian units are still isolated behind the lines of the Russians/pro-Russian forces, which means they will have to be allowed to withdraw without being fired upon, which in turn requires restraint and discipline from both sides, which is no sure thing. It is also clear that both sides are using the ceasefire to reinforce their positions, with reports of armor and other equipment continuing to cross the border from Russia and of Ukrainian reinforcements arriving from the west and north.

Moreover, Ukrainian forces are still present in the outskirts of Donetsk and control the airport. Securing Donetsk, and being able to defend it going forward, is critical to the separatists’ plans for a breakaway state of Novorossiya, as is control of the airport. It is therefore difficult to see how they can accept the presence of Ukrainian forces that close to their self-declared capital. Likewise it is difficult to see Kyiv agreeing to withdraw its forces from those hard-won areas unless compelled to do so by force.

In addition, there is the problem of the southern part of the conflict zone, particularly the city of Mariupol. While Ukrainian reinforcements have been arriving in the city over the past week, my impression is that the size of the force defending the city is not large and consists mostly of volunteer units, particularly the Azov Battalion. That does not mean that the Ukrainians don’t intend to mount a vigorous defense of the city – I assume that they do, and I expect that an assault on the city would be destructive and bloody, like most urban battles. But it increases the likelihood that the separatists, and perhaps Moscow, think the city can be taken relatively quickly.

Indeed, many separatists have made clear that they want to build on the momentum of their successes over the past two weeks and press ahead into Mariupol. They have taken Novoazovsk, but that is a small town of only 12,000 inhabitants and with no port facilities to speak of. Mariupol, in contrast, is a medium-sized, industrial city of some 500,000, with steel mills, chemical plants, shipyards, and a significant port. This, too, increases the likelihood that the separatist leadership, or perhaps just a local commander, will decide to violate the ceasefire and attack the city.

Finally, the current disposition of forces does not give Moscow a land corridor to Crimea, and neither does it solve Moscow’s red-line issues: Ukraine’s relationship with the West and NATO’s presence near its borders.

Contributing to the disposition of military forces problem is the fact that the parties to the conflict appear to be far from a political settlement. Kyiv claims that the peace plan agreed to in Minsk yesterday will preserve the country’s territorial integrity, so presumably it is insisting on some kind of continued authority in the Donbas. While the details of the plan have yet to be made public, The New York Times reported the following:

The 14-point peace plan includes some references to the cease-fire itself, some practical steps toward returning government control to the southeast Donbass region and some nods toward future political changes, according to a summary published by the Ukrainian national information agency… It includes amnesty for those who disarm and who did not commit serious crimes, and the exchange of all prisoners. Militias will be disbanded, and a 10-kilometer buffer zone — about six miles — will be established along the Russian-Ukrainian border. The area will be subject to joint patrols. The separatists have agreed to leave the administrative buildings they control and to allow broadcasts from Ukraine to resume on local television.

I think it is highly unlikely, however, that the separatist militias are going to disband or disarm, and I seriously doubt that Ukrainian volunteer units (if that is what is meant by militias) will either. I am even more doubtful that the separatists will allow Kyiv any kind of authority in the areas currently under their control. And while Russian regular forces might withdraw, the pro-Russian irregulars will not, and neither will the armor, MLRS systems, SAMs and anti-aircraft guns, or other heavy military equipment that have been coming into the region since March.

Finally, it is very unlikely that either Moscow or the separatists will allow Kyiv to exercise any meaningful control over the border. What is possible – eventually, at any rate – is a demilitarized zone monitored by the OSCE along the border. But any Ukrainian “joint patrolling” in the zone, or other presence along the border, is going to be entirely pro-forma. In practice, control on one side will be exercised by Russian border guards, and on the other by border guards of Novorossiya.

As I prepare to post this, I am already seeing tweets reporting on the shelling of Ukrainian positions on the outskirts of Mariupol. Whether this portends a full breakdown of the ceasefire is not yet clear.