Contemporary society’s perception of past wars is almost exclusively driven by historic sources such as film recordings, photographs and written documents that are presented in mass media. However, the legacy of these wars is still present throughout European soil and waters, including the Baltic Sea. The marine waters of every Baltic Sea state contain warfare materials. Resulting risks may be direct and short-term. Fishermen, divers, offshore wind farm constructors and beachgoers can potentially be exposed to their remains while performing their daily work or while collecting objects in the surf. Other potential effects might be indirect and long-term such as the accumulation of carcinogenic toxic substances and their metabolites in the marine food web. Since 1974 Contracting Parties of the Helsinki Convention are seeking to address the increasing environmental challenges from human activities and that were having a severe impact on the marine environment. This includes the protection of the Baltic Sea from all sources of pollution, and thus munitions in the Baltic Sea are addressed by HELCOM since 1993. The convention commits the signatories to take measures to conserve habitats and biological diversity and for the sustainable use of marine resources. In addition, warfare materials potentially constitute a hazard and an obstacle for the utilization of the sea floor for economic purposes. The global ocean economy is predicted to double in size by 2030, as compared to 2010 (OECD 2016). In the Blue Growth Strategy laid out by the European Commission the economic potential for the extended economic usage of the oceans was recognized and focus was placed on five blue growth sectors. Two of these sectors (ocean energy and seabed mining) require the ability to safely access large areas of the sea floor (European Commission 2017). In order to exploit the economic potential of the ocean energy and seabed resources sectors, the detection and removal of warfare materials in affected areas will become increasingly important (European Parliament 2021). Recently, numerous HELCOM Contracting Parties supported increasing the knowledge concerning warfare materials in the Baltic Sea and their effects on humans and the marine environment of the Baltic Sea. As a result of national, regional and international scientific research the understanding of the issue grows and consequentially numerous recommendations are published on how the warfare materials challenge can be addressed. However, international coordination is necessary to identify synergies and to avoid a duplication of efforts. This report provides the current state of knowledge on warfare materials in the Baltic sea based on recent research projects.