In 2001, on the slope of Uppsala Castle, a mass grave associated with the Battle of Good Friday between Danes and Swedes in 1520 was discovered. According to osteological examinations, at least 59 male individuals between the ages of 25 and 34 were buried. The demographic profile showed similarities to other European war-related skeletal remains (Laine, 2020; Kjellström, 2005). According to historical accounts, the Swedish forces were primarily peasants, whereas the Danish soldiers were mercenaries from Germany, France, and Scotland (Sandstedt, 2003). It has been stated that, on the Danish side, around 2,000 men were killed, and the losses on the Swedish side were even greater (Berg, 2000). In this project, we aim to analyze genomic data produced from 59 individuals from the aforementioned mass grave. For this, in-depth genome-wide analysis, with a focus on demography, genetic kinship, and molecular sex, will be applied to genomic data generated within the project. This project will provide the first insights into the genetic architecture of warfare in 16th-century Sweden. It will further shed light on archaeological and historical questions about the genetic structure of the remains and the unresolved questions, i.e., whether the Danish army consisted of Danish soldiers or mercenaries. The proposed project will further produce rich material for reuse by archaeogenetics and archaeology communities and thereby significantly contribute to the field.