ENEvents of the summer 2020 in Belarus and the measures taken by the official Minsk afterwards led to an increase in alert in Lithuania with respect to military or hybrid provocations from its neighbour. The most important cause of growing security concerns, however, is related not so much to the unpredictability of A. Lukashenka but has to do with the actual and potential military integration of Belarus’ into Russia’s military structures. The self-imposed isolation from the West of A. Lukashenka, desperate to remain in power, further increases Moscow’s leverage over the already heavily dependent regime. The potential of further military integration between Belarus and Russia is seen as an additional argument for the rapid implementation of NATO decisions taken in recent years to reinforce security of the Baltic states and deter potential aggression from the East. Lithuanian authorities reacted to the Belarus 2020 crisis by reinforcing defence capabilities, intensifying cooperation within NATO, and within the EU, especially after the forced landing of the Ryanair Athens-Vilnius flight in Minsk and the weaponisation of migration flows by Belarus. The 2020 crisis marks a milestone, when the hopes of convincing A. Lukashenka to open up to the West and reform the country to increase its autonomy from Russia have been finally abandoned. Keywords: Belarus; Lithuania; security; Belarus-Russia military cooperation.