This comparative case study examines alliance memberships’ impact on two states’ strategic culture. It focuses on changes in Danish and Norwegian strategic culture during 2008-2012, examining if and how NATO membership and specifically NATO's 2010 strategic concept impacted potential changes in the states’ strategic culture. The dependent variable, strategic culture, is broken down into three sub-beliefs used to identify relevant content in the analysed material. Using national defence white papers published before and after the strategic concept as material, a qualitative content analysis is then conducted to identify changes to the sub- beliefs before and after the release of the strategic concept. The sub-beliefs are also used to analyse the 2010 strategic concept to identify themes, which are then compared to changes in strategic culture found before and after the release of the concept. The analysis found that after the release of the concept all three of the Norwegian sub-beliefs changed in several ways that were consistent with the main themes identified in the concept, as well as using the concept as justification for changes and prioritisations in policies. Based on this the thesis makes the claim that the strategic concept likely impacted Norwegian strategic culture in several ways. While Danish sub-beliefs did change in some areas that were consistent with themes in the strategic concept, the changes were not conclusive enough to make the claim that the strategic concept had any meaningful impact on Danish strategic culture.