The 2022 Russian invasion of Ukraine received widespread international condemnation. In Slovakia, the invasion became a subject of much political discussion with large number of MPs openly advocating Russian interests. This study investigates Slovak political discourse on Facebook in the weeks before and after the invasion began. We examine the discourse through the lens of Discourse Network Analysis, combining qualitative content analysis of MPs’ Facebook posts with quantitative bipartite social network analysis. During the two weeks, we retrieved all (n = 1880) posts from all (n = 117) MPs who had an active public Facebook page. We manually coded all posts and created a bipartite discourse network consisting of MPs connected to each other via shared discourse codes in two timepoints. We performed a series of exploratory analyses that identified the content of the political discourse, the structure of the political discourse network, and the mechanisms driving the change of the political discourse network. Our results show that the invasion dramatically changed political discourse in Slovakia, with the domestic coalition-opposition struggles losing prominence among the invasion-related topics. The structure of the political discourse network showed a strong coalition-opposition split. While coalition MPs had largely pro-Ukrainian sentiments, opposition MPs largely communicated pro-Russian propaganda. A cluster of opposition MPs consistently spread conspiracy theories both before and after the invasion began, supporting a “conspiracy singularity” theory—the tendency of actors to spread multiple different conspiracy theories and interconnect various conspiracy theories into one overarching narrative. The change of the discourse network at the beginning of the invasion was largely driven by the agenda setting of several parties, agenda reinforcement, and increasing political polarization. We discuss our findings in relation to the previous research on the spread of conspiracy theories among politicians and the polarization of political discourse during the invasion, and we suggest implications for future research.