What would it take for a ceasefire between Russia and Ukraine to hold?

This op-ed was first published by  IPI Global Observatory 18 March 2025.

We know a lot about how to implement a ceasefire, as well as the factors that influence the likelihood that it will be successful or not.

In the case of the Russian war on Ukraine, America has proposed a 30-day ceasefire, with the hope that it can start a process that can end the war. Ukraine has agreed to the ceasefire but President Putin raised questions regarding how such a ceasefire will be monitored and how breaches of the ceasefire will be managed? These are the aspects of ceasefire monitoring that the United Nations (UN) and others have a lot of experience with.

The technical elements those involved in the ceasefire negotiations would need to make decisions on include agreeing on a line of separation, a buffer zone, an exclusion zone and a ceasefire monitoring and verification mechanism.

Line of separation

Typically, a ceasefire has as its baseline a line of separation or ceasefire line. This is literally a line on a map that separate the two sided from each other. Crossing the line by land, sea or air, will imply a return to war. In Cyprus, for example, this is the so-called green line that separate the north from the south. In Lebanon, a blue line separated Israeli and Hezbollah forces. The line will typically be determined by the military position of both sides at the time of the agreement. The ceasefire line is agreed for the purpose of the ceasefire, and it is thus not meant to prejudice any future peace agreement. The front lines in the Russian war on Ukraine currently extends over approximately 2000 kilometres, and mapping out every kilometre will be a substantial, but necessary first task.

Buffer zone

From the line of separation there is typically a buffer zone of several kilometres that neither side may enter by land, sea or air. This is an agreed distance of de-militarised no-man’s land, to create a buffer zone between the two armies that avoid accidental fire or other incidents that can spark confrontations and reignite the war.

Exclusion or limitation zones

From the line of separation there is also typically an exclusion or limitation zone with provisions that prohibit different types of heavy weaponry, ships, aircraft or drones from being deployed or operated within a certain distance from the line of separation. The aim is that the warring forces should not have weapons positioned close enough to each other to be able to shell each other, and that any hostile manoeuvres will have to start from a distance that allows the other side time to react.

Ceasefire monitoring and verification mechanism

Ceasefires are entered into by countries or parties at war with each other. They don’t trust each other and thus need a means to independently verify that the other side is complying with the agreement. A ceasefire monitoring mechanism typically consist of a body that oversee the mechanism, and a means to monitor compliance as well as to investigate breaches of the agreement.

The body that oversees the agreement – often called a joint ceasefire monitoring commission - typically consist of representatives of both sides and it can be chaired by a 3^rd party, often the mediator acting as a guarantor or an organisation like the UN. It will review compliance reports and make decisions about how to handle alleged breaches. The mechanism will establish lines of communication between the parties, for example by deploying liaison officers, that will enable quick and secure communication. This kind of arrangement is critical to manage incidents that need urgent steps to de-escalate a situation in a context of deep mistrust between the parties.

In most ceasefire arrangements to date, unarmed observers monitor the line of separation and the buffer zone and verify that the parties are not in breach of the exclusion zones. If there are any alleged breaches of the agreement the 3^rd party, or a joint mechanism, investigate and report back to the body that oversee the agreement. All these mechanisms are meant to re-assure both sides that the actions of the other side are being independently monitored and verified. 

It should be stressed that none of the ceasefire operations deployed to date have been mandated to use force to prevent either side from attacking each other. There is a common misperception that UN peacekeepers in, for example, Lebanon, is supposed to use force to prevent Israel from attacking Hezbollah or vice versa. This is not the case. Ceasefire monitors are per-definition unarmed, or lightly armed to protect themselves, and their role is limited to helping the parties to the agreement to monitoring compliance with and facilitating the implementation of the ceasefire.

Who will monitor and verify compliance with the ceasefire?

Who can perform the role of a neutral 3^rd party that can assist Russia and Ukraine to implement a ceasefire? It would need to be an organisation or an arrangement that both sides trust to be neutral, as well as professionally capable to verify the compliance of the other side.

An important distinction needs to be drawn between neutral peacekeepers that monitor and verify a ceasefire agreement, and other forces that may be deployed as a security guarantee for Ukraine or Russia. Both Russia and European leaders have referred at times to their own forces as peacekeepers, but this is a political rather than technical use of the term. From the perspective of a ceasefire implementation arrangement, European forces deployed in Ukraine as a security guarantee for Ukraine, or Korean or other forces deployed in support of Russian forces, would have to comply with the same ceasefire arrangements as the forces they are allied too. It would not be tenable for such forces to guarantee the security of one side and be neutral 3^rd party peacekeepers at the same time. Security guarantees will be an important aspect of a successful ceasefire and eventual peace agreement, but such forces should not be confused with neutral ceasefire observers that may be deployed to help monitor and verify a cease-fire agreement. That means that a body like the European Union, NATO or the Collective Security Treaty Organization (CSTO) that is associated with either side would be automatically ruled out. That leaves the UN, OSCE or a special arrangement established for this purpose.

At this early stage in the negotiations, the United States (US) and Ukraine appear to favour the latter option. President Zelensky has suggested that a ceasefire between Russia and Ukraine can be monitored by US satellites and drones. It is unclear if the US, that is providing arms and intelligence to Ukraine, would be trusted by Russia to act as the neutral 3^rd party that verify compliance of the agreement. There are also technical limitations to satellites and drones such as bad weather and cloud cover. Most importantly, such an arrangement seems to lack a mechanism for investigating alleged breaches and to manage incidents in the field. Past experience, including in Donbas, indicate that there are always many incidents and alleged breaches that require daily follow-up. If US remote monitoring of the ceasefire is not sufficient on its own, an alternative is to consider monitoring by the UN or the Organisation for Security and Cooperation in Europe (OSCE).

Russia, Ukraine and most the stakeholders in the war are members of the OSCE. It has experience with ceasefire monitoring, including in Ukraine where it monitored the Minsk ceasefire agreement in the Donbas between 2014 and 2022. A challenge with the OSCE, however, is that decisions are consensus based and non-binding. A further challenge is that many, if not all the members of the OSCE has come out in support of one or other of the parties to the conflict. So, an OSCE ceasefire mission will probably have to base its neutrality on establishing monitoring teams that consist of citizens of countries that have been aligned with either side, so that they can monitor each other. Deploying and managing such a mission will be significant challenge.

The UN is the international organisation with the most experience with deploying and managing ceasefire observer missions. It also has access to a global pool of troop contributing countries from which observers could be drawn that may be acceptable to both sides. It has a well-oiled mechanism for deploying, overseeing and funding such a mission. Most importantly, UN missions are deployed and overseen by the UN Security Council where Russia, the US, China, France and the United Kingdom are permanent members with veto powers. Although Ukraine is not a member, the presence of key allies like France and the United Kingdom and the role of the US as mediator and guarantor, will probably give them sufficient confidence that their interests will be protected in the UN Security Council. The UN Security Council will be asked to endorse a ceasefire agreement, so if the parties want the help of the UN to independently verify compliance, that would be a natural role that the UN has played in many similar contexts in the past.

The most likely mechanism is some kind of combination of these options. Monitoring a line of separation, as well as buffer and exclusion zones 24/7 over approximately 2000 kilometres will be a huge challenge. It will require the use of technology such as satellites and drones, but it will also require boots on the ground to deal with incidents, manage exceptions like allowing civilians access to the buffer zone for specific purposes, and to investigate alleged violations. This can be managed by a joint mechanism made up by both sides and perhaps the guarantor. Russia and Ukraine have the advantage of already having a presence, knowing the terrain and being able to communicate.

Past experiences with such joint mechanisms show, however, that the parties often use such mechanism as a micro-battle space where they withhold or manipulate information and continuously spar on every issue. Deploying civilian or unarmed military observers by a neutral 3^rd party like the UN could help to overcome these trust issues and facilitate the working of such a joint mechanism. Deploying an international operation takes time and sending more than a few dozen UN experts to support the first phase of the process may thus not be an immediate option. However, if the ceasefire becomes more permanent, and if Russia and Ukrainian find it challenging to monitor the ceasefire on the ground on their own, then deploying a UN ceasefire observer mission to facilitate the process could be an option worth considering.

Factors that influence the success of ceasefire arrangements

With 80 years of UN experience and an even longer history of other experiences to draw on, we can say that there is a well-established understanding in policy and academic circles of the factors that influence the likely success of ceasefire agreements. Two factors stand-out above all else: legitimacy and credibility.

First, the degree to which the agreement and arrangements are perceived as legitimate and viable are critical to the success of the outcome. Do the parties to the agreement and other key stakeholders have a shared understanding of what they want to achieve, and how they will go about it? In other words, is there sufficient political commitment and public support to make the ceasefire a viable project.

Second, the extent to which the ceasefire mechanism or operation is perceived to be capable of credibly carrying out the monitoring and verifying tasks entrusted to it will largely influence both compliance and trust. Does the arrangement have the leadership, staff, equipment and resources necessary to monitor and verify compliance, investigate breaches and act assertively to maintain confidence when critical incidents raise emotions and undermine trust. In other words, do the parties to the agreement and other key stakeholders have sufficient confidence in the credibility of the arrangements to hold up under stress.

Regardless of what kind of mechanism is agreed on to oversee a cease-fire agreement between Russia and Ukraine, it will be a momentous task. It will require both sides and the mediator to develop a shared understanding of the critical elements that need to be in place to ensure success, as well as a degree of pragmatism and flexibility to resolve problems as they arise. The most important ingredient will be sustaining the political will to make it work.