This thesis critically examines the role of external actors in managing the rivalry between Israel and Iran from 2015 to 2025. The study is guided by four key objectives: to assess the extent to which external interventions have succeeded or failed in managing escalation; to analyze the strategies employed by external actors in conflict management; to evaluate the Joint Comprehensive Plan of Action (JCPOA) as a tool of conflict management; and to examine the broader lessons the Israel–Iran rivalry provides for international conflict management. The study adopts a qualitative research design, relying on documentary analysis of policy documents, official reports, international treaties, and relevant scholarly literature. Theoretical analysis is informed by realist theory, which helps explain the strategic behaviour of both regional and external actors within the rivalry. The qualitative approach is considered appropriate as it allows for an in-depth understanding of meanings, patterns, and relationships embedded in international conflict dynamics, rather than numerical measurement of variables. Findings reveal that the Israel–Iran rivalry between 2015 and 2025 has been sustained through proxy warfare, targeted military strikes, cyber operations, and diplomatic containment strategies. Iran’s approach is largely anchored on the use of non-state allies across Lebanon, Syria, Iraq, and Yemen, while Israel relies on intelligence operations, precision airstrikes, and the disruption of Iranian regional influence. Despite persistent tensions, both states have largely avoided full-scale war through deterrence and calibrated escalation. The study further finds that external interventions have produced mixed outcomes, as they have contributed to both temporary de-escalation and unintended escalation. The continued expansion of proxy networks, technological advancements in warfare, and shifting regional alliances increase the risk of miscalculation and potential escalation into open conflict. The study recommends that foreign interventions should prioritize the strengthening of regional security dialogue frameworks involving Gulf Cooperation Council states, Turkey, and other regional stakeholders. An inclusive regional security architecture would help reduce bilateral tensions and distribute responsibility for conflict management more effectively.