Democracies are Janus-faced. While they do not fight each other, they are frequently involved in militarized disputes and wars with authoritarian regimes. The article argues that these two empirical findings on the dyadic level are under-theorized. After reviewing the prevailing explanations for the `democratic peace', the article presents a social constructivist perspective starting from the so-called normative approach. To a large degree democracies create their friends and enemies — `us' and `them' — by inferring either defensive or aggressive motives from the domestic structures of their counterparts. On the one hand, they follow behavioural norms externalizing their internal compromise-oriented and non-violent decision rules in their interactions with other democracies. On the other hand, the presumption of potential enmity creates a realist world of anarchy when democratic states interact with authoritarian regimes.