While lessons from the field of conflict resolution suggest that the parties must ultimately resolve their differences between themselves (often with third party assistance), external actors can use their influence and resources to generate positive incentives or negative pressure to seek a negotiated settlement and to increase the viability of a durable outcome. The purpose of this article is to examine and analyse the policy instruments that can be harnessed as sanctions and incentives to support peacemaking.

External actors' policy instruments can be conceived within a spectrum of different modes of influence, each reflecting a different logic of how change can be achieved and what degree of 'leverage' is required to achieve it (see "A spectrum of influence" table at the end of this article). At one end of the spectrum are the most coercive measures, from outright force to various forms of restriction or punitive pressure. Lower down are measures that are less coercive but based on a similar logic of reward and punishment, aimed at encouraging changes in behaviour through offering positive incentives. Towards the bottom of the spectrum are non-coercive and non-conditional measures to facilitate changes in the parties' relationships and mindsets, such as the creation of forums, training or tools for negotiation for parties that are receptive to engaging in negotiations.

Clearly, the boundaries between different modes of influence are not always distinct. Furthermore a policy instrument may straddle different modes of influence. Security guarantees, police missions or border assistance, for example, may be seen as an incentive or enabler, yet are also underpinned by a capacity for force.

Unlike facilitation and force, many of the incentives and pressures in the middle of the spectrum are wielded according to a logic of conditionality. They are linked with their target's actions: "if you do x , then we will do y " or "we will (continue to) provide x , unless you do y – in which case, we will take x away." Thomas Schelling observes that their aim may be 'compellence' (do x), 'negative compellence' (stop doing x) or deterrence (don't start doing x). In using conditionality, external actors seek to alter their target's cost-benefit calculus by supplying benefits conditionally upon changes in behaviour or policy.

In theory, conditionality is successful if the value of the benefit exceeds the costs of compliance with attached conditions or expectations. Yet these are seldom straightforward calculations. Armed conflicts pose special difficulties for any assumption of rational choices about costs and benefits. First, the parties may be motivated by deeply held ideological or value-based goals not easily amenable to change from external pressure or incentives. Second, the dynamics of entrapment – when parties remain committed to apparently failing strategies because of the scale of resources and commitment they have already invested in them – can create barriers to altering strategic direction.

Furthermore, the success of all these policy instruments for peacemaking is dependent on how they interface with the wider conflict dynamics. There is a complex interplay between conflict parties' pursuit of their own goals through external actors and the actual actions of external actors. A persistent challenge that must constantly be managed is the parties' attempt to manipulate external intervention to their advantage. The leaders of state parties to a conflict may have a considerable advantage in this effort, as is revealed in the case studies on Sri Lanka, Israel, Georgia, Uganda and Sudan. Yet non-state actors can also play the game. While sanctions and incentives may be intended to change the cost/benefits equation of the parties to a conflict and thus influence their decision-making calculus in favour of ending their armed conflict, very often the principal outcome is to add to the symbolic politics of conflict.

International organisations or foreign governments sometimes intervene militarily in a conflict situation, usually under the banner of protecting populations and/or removing the leaders who threaten them. Consensually deployed multilateral peacekeeping missions to supervise truces (or non-consensually in cases where there is a void of effective authority) are not generally used as an instrument of coercion. Yet the direct or implied threat of a non-consensual deployment of force is occasionally used in a coercive diplomatic approach to imposing a settlement. They may, however, be problematic for negotiations. For example, the US's credible threat of a military invasion of Haiti in 1994 helped to secure a last-minute agreement but it was almost scuppered when it became apparent the invasion was already underway.

Next along the spectrum are measures – threatened or applied – to pressure one or all of the conflict parties to modify their behaviour or position. They work by raising the costs of intransigence, comprising an array of formal sanctions as well as other forms of condemnation and pressure, including legal and diplomatic sanctions as well as other largely symbolic protests or penalties.

Formal sanctions are one of the principal instruments available to the international community to enforce international law, norms and standards. Imposing such measures is typically high on the agenda of international responses to conflict, often with the goal of getting their targets to cease unacceptable behaviour, rather than to encourage them to negotiate a settlement per se. Usually enacted by the body of an international organisation (such as the UN Security Council), they are occasionally undertaken by a group of states or unilaterally by one influential state or group (such as the US or EU). Some sanctions may originate in international civil society activism, such as sports or cultural boycotts like those enacted against apartheid South Africa and threatened against China more recently.

Usage has evolved quickly since the 'sanctions boom' of the 1990s. UN sanctions targeting war economy commodities (such as diamonds, oil or timber) have aimed at inhibiting war-making capabilities. Targeted or 'smart' sanctions aim to minimise the harmful effects on civilian populations, which were typical of comprehensive economic sanctions. Measures such as travel bans and asset freezes enable the UN and others to target individuals and non-state entities. However, sanctions – even targeted ones – are not precision tools and their impact varies widely. They are sometimes perceived (and used) as symbolic sanctions and their main impact is stigmatisation: 'naming and shaming' targets rather than impeding their activities or extracting direct concessions. Even if mainly symbolic, the imposition of sanctions can have a powerful effect in signalling international disapproval of those violating international norms.

While sanctions are never sufficient as a conflict resolution tool (not themselves addressing the root causes of a conflict or the need for dialogue and problem-solving), they may play a role in a conflict resolution process, as explored in the next chapter. The threat of sanctions may be influential in deterring egregious and escalatory behaviour. In some cases they sufficiently weaken parties' strategic military, economic or diplomatic position so that they recognise they have more to gain by entering the process than by eschewing it, as seen in Sudan and Côte d'Ivoire.

As Risse, Ropp and Sikkink have argued, sanctions, especially those originating in civil society, may have a 'socialising' effect. They send the message that if particular behaviour persists then the target may be excluded from its chosen 'reference group' (such as the 'West' or the 'international community'). Even if the parties enter into talks simply to simulate compliance with international pressure, engaging in 'talking the talk' of compromise, human rights and peace may ultimately have a deeper-rooted impact upon conflict-affected societies than initially assumed, as the South Africa case reveals.

Yet sanctions are rarely crafted as an element of a strategic conflict resolution framework. As such, they often have a number of unintended consequences on the conflict – in part due to their bluntness and inflexibility on one hand and the perception of bias and inconsistency on the other. They are often perceived as bargaining chips in wider political games. Many of the cases reveal that sanctions fail to achieve specific behavioural change and inadvertently escalate conflict dynamics. They can harden or entrench conflict attitudes and behaviour, as in the 'rally-around-the-flag' effect identified by Johan Galtung. These negative effects tend to be especially strong where sanctions are popularly associated with one side's efforts to isolate and weaken an adversary, such as the Commonwealth of Independent States' sanctions on Abkhazia.

Once established, usually through a long and difficult process, lifting sanctions can be complicated. Sometimes those targeted with sanctions do not believe that they will be lifted even if they comply (as happened at certain points in Iraq and Sudan). Furthermore, while the threat of sanctions may be effective for encouraging leaders to change their approach, once applied they tend to sit heavily on a process. Often there is little reason for the parties to change tack, as they are already paying the price of isolation.

Many negative sanctions make engagement difficult or impossible, especially where they are designed without reference to specific conflicts. For example, terrorist listings, used to punish or isolate armed groups deemed to be international security threats, are also applied to many groups associated with domestic armed conflicts. While such lists express clear disapproval, they are typically perceived by the proscribed group as an attempt to de-legitimise their goals rather than their methods. This can sometimes entrench militant positions and weaken factions willing to explore a political strategy leading to conflict settlement by sealing off choices and avenues for dialogue.

The effectiveness of sanctions as a tool of persuasion seems to depend on: (a) how the leaders of the belligerent groups respond and whether they are concerned about the consequences of the sanctions on the public or themselves; (b) the credibility of the threatened sanctions and whether they will be implemented and enforced; (c) the credibility of the sanctioners and particularly whether important allies will cut off their support; and (d) the wider political context and how it has shaped the expectations of the parties.

Measures can be applied to encourage or persuade one or all of the parties to a conflict to cooperate by introducing rewards for compliance. Incentive-based measures can be used to foster favourable conditions for engagement, encourage progress in a peace process, support implementation of agreements and generate wider support for peace.

The three principal sets of rewards are: (a) those that respond to economic needs, (b) those that respond to political needs for legitimacy and recognition, and (c) those that respond to needs for assurances and security guarantees.

Economic benefits like development aid can be deployed to support the resolution of conflicts. The conditional use of donor assistance in peacemaking or peacebuilding has been termed 'peace conditionalities.' As well as supporting conflict prevention efforts or post-settlement peacebuilding, they may be wielded in the midst of a peace process to offer the prospect of a 'peace dividend' (economic benefits linked to peace and stability). Yet, as Jonathan Goodhand has observed, efforts to 'buy peace' rarely succeed because aid is seldom a pre-eminent factor in the transition from war to peace, operating at the margins of the political economy of war. The measures on offer may not be as attractive to the targets as anticipated. Incentives such as reconstruction and development assistance rarely trump political aspirations. The request to give up long-held values in exchange for an economic benefit can risk being interpreted as a bribe. Furthermore, peace conditionalities are embedded in the wider context of donor conditionality and are subject to the same debates over appropriateness and sovereignty.

The parties' political aspirations often lead them to value external relationships, making diplomatic relationships a useful resource in peace processes. Valued for legitimacy, prestige and recognition, they can be utilised to encourage or reward positive change (as well as the reverse). On the micro-scale, non-state actors as well as governments benefit from symbolic acts, such as when former US President Clinton allowed representatives of Sinn Féin (widely viewed as linked to the Irish Republican Army) to visit Washington, opening new channels for pro-agreement Irish Americans to exercise influence with them. On the macro-scale, the opportunity to be recognised as a full member in good standing of international institutions or multilateral groups can be a powerful incentive (if partly because of associated economic benefits). This has been notable in the European space, for example, where the potential to join the EU has been a powerful catalyst for change (if not harnessed to maximum effect in Cyprus, see page 35).

Another important tool that is both incentive and enabler is the externally-given guarantee deployed to reduce threats, enhance security, and build confidence. One of the significant obstacles to reaching and implementing peace agreements is that parties lack sufficient trust in their opponents to believe that they will follow through on their promises. External actors – whether international organisations, groups of states, or influential third parties – can offer various forms of guarantees aimed at encouraging the parties to settle their differences. 'Political guarantees' are often an integral aspect of peace agreements and involve political and practical support to assist implementation and assurances that external parties will use their influence to foster parties' compliance with the terms agreed. 'Security guarantees' typically involve external assistance in demilitarisation of the conflict, ranging from ceasefire monitors to implementing disarmament, demobilisation and reintegration (DDR) processes.

As with sanctions and pressure, applying incentives in the context of peace processes is fraught with risks and dilemmas. In an era of highly internationalised peacemaking, there are many benefits to signing on to a peace process in bad faith, to extract rewards or simply to meet international expectations. There is sometimes a dysfunctional over-incentivisation to participate in peace talks, for example when excessive per diems are offered to the negotiators or when agreements build in opportunities for securing personal financial interests. The introduction of external incentives can distort the motivations for serious engagement with an adversary, placing the emphasis on bargaining for concessions from third parties. A further problem, as Nathalie Tocci explains in her article, is that different actors within a target group value benefits differently – thus incentives and conditionalities can trigger internal fissures within a group and the resulting decisions may not be the expected outcome.

The success of external incentives seems to depend on their capacity to encourage and amplify the parties' own incentives for offering concessions to their adversaries, as Anthony Regan explores in the Bougainville study.

The facilitative end of the spectrum concerns measures to support the parties to a conflict to negotiate a solution. Techniques may include confidence-building, building the capacity to negotiate, and facilitating dialogue and reconciliation at different social and political levels.

While incentives and disincentives can lead to change by altering the protagonists' decision-making calculations, in the short term they do not change the mindsets that led to the violence in the first place. This transformation can typically only happen through a process of engagement between the parties. Such engagement can generate changes in their relationship and the wider social dynamics of the conflict, recognition that the old assumptions are no longer applicable, and new ideas about options and alternatives that help to reframe the conflict. Training and technical advice to the parties' negotiators can significantly help the effectiveness of the negotiations and the parties' ability to craft durable compromises. Because facilitative tools depend upon the parties' own readiness to change, they may not produce quick results. Yet they are typically crucial for the success of the peace processes, as is explored in greater depth in the following chapter.

A spectrum of influence