The Syrian ceasefire agreement brokered by Russia and the United States which came into effect on Monday night already looks fragile, with key Islamist combatant parties excluded and other opposition groups believing they will be targeted as Islamists. US Secretary of State John Kerry has said this ceasefire may be the last chance Syria has of working towards peace in the war-ravaged country.

The ceasefire itself is tenuous, intended to be renewed every 48 hours for a week, after which further co-operation may be possible. However, Syrian opposition groups note that the exclusion from the ceasefire of Jabhat Fateh al-Sham group — formerly the al-Qaeda-allied Jabhat al-Nusra — will expose other opposition groups that have worked with it to Russian air force and Syrian army attacks.

Excluding Islamic State and Jabhat Fateh al-Sham from the ceasefire has effectively reduced the ceasefire to about a third of the anti-regime groups. With Syrian leader Bashar al-Assad having said that he intends to “recover” all of Syria from “terrorist groups”, the ceasefire appears to be viewed by the government as an opportunity to focus attacks against the two most powerful anti-regime groups, leaving the myriad smaller ceasefire groups to be dealt with later.

While the “moderate” ceasefire groups have welcomed the ceasefire as an opportunity to relieve civilians, particularly in the besieged city of Aleppo, it is not clear they view the ceasefire as anything other than a pause in hostilities. There must, from their perspective, be agreement for regime change before there can be peace.

Now in its fifth year, of a population of 23 million, the Syrian civil war has already killed up to half a million people and displaced 6 million more within Syria and a further 3 million fleeing the country. The city of Aleppo, which is at least 4500 years old and much of which dated to the 12th-16th centuries, now lies in ruins, while other several world heritage sites, such as Palmyra, have been either partially or totally destroyed.

At the centre of a possible peace agreement is the future of Assad as president. With the Syrian government in a relatively strong position and with Russian support, it has no interest in bargaining on this issue. Yet, while there is now some agreement among anti-regime forces that a post-peace agreement government would include current regime representatives, Assad’s personal involvement remains, for them, an insurmountable hurdle.

That the US and Russia brokered the ceasefire, and both have been actively supporting competing camps and targeting different groups, there is also an element in which the Syrian conflict has become, in part, a proxy war between one superpower and a once and again aspiring superpower. In part, therefore, whether a peace agreement becomes possible, or whether war will continue, will depend on the continuing active involvement of these two external actors.

The US is unlikely to want to allow Russia to dominate this pivotal Middle Eastern country, and Russia intends to continue with its “return to greatness”, including influencing affairs in Syria. Assuming there will not be an inclusive, Assad-less “government of national unity” it therefore appears unlikely that one side or the other will be able to fully overcome the other.

Significant proportions of Syria’s warring groups are geographically divided, with pro-government groups tending towards the west and south and anti-government forces to the north and east. The country therefore appears to be heading towards settling into a permanent division, with control of what is left of Aleppo being the key prize.

As for the partial ceasefire, it is a truism of conflict resolution that, without a larger peace agreement to cement it, a ceasefire is only good for that time its lasts. This ceasefire looks, at the moment, to, at best, be a day-by-day proposition.