Increasing concerns about new threats related to a possible major accident on a nuclear power plant or a tactical nuclear explosion, linked with the war in Ukraine, impose to EU Countries to improve their current capabilities to prepare for and respond to these possible large-scale accidents. The need for advanced technologies, interoperable risk assessment tools, and comprehensive emergency coordination strategies has never been more critical. GUARDIANS will deliver advanced, cost-effective technologies, and strategies to improve disaster emergency management in Europe. The project will enable the development of advanced radiological technologies (radioactive gas sensor, active dosimeter network), innovative and scalable strategies for triage (video analyses, digital triage), decontamination, and medical countermeasures (hydrogel, new strategy for stable iodine distribution). Autonomous means such as drones and robots equipped for radiological measurements and enhanced observation capabilities will increase overall responsiveness. A central web-platform GUARDNET, built upon existing operational tools, will facilitate real-time information processing, synthesis, mission management, and simulation services, to support decision-making. The active participation of first responders/receivers and decision-makers, along with the execution of two field tests and the assessment of the alignment between population needs and authorities' response strategies will ensure that GUARDIANS produces a new and enhanced operational capability to respond effectively to a radiological or nuclear emergency. GUARDIANS will significantly enhance European Member States' ability by providing stakeholders with state-of-the-art capabilities, innovative technologies, and effective coordination strategies. This will accelerate the decision-making process, reduce intervention times, and mitigate human and environmental impacts through improved protection of populations and infrastructures.