The authors of this study argue that the current security situation in Europe resembles a glass that is either half-empty or half-full and show that, while the Vienna Document CSBM agreement has been surprisingly effective in the past, today it is faced with not only serious challenges but also great opportunities to improve in the future. The authors explore 13 research questions: 1. How do contextual factors in the existing security environment impact on the effectiveness of the Vienna Document's CSBMs? 2. To what extent are the main objectives of the agreement being met? 3. To what extent are the norms and rules being complied with? 4. How effective are the Vienna Document's CSBMs during military crises and conflicts? 5. How effective are the Vienna Document's CSBMs with regard to internal armed conflicts? 6. What should be done about non-compliance? 7. How are the benefits of cooperation distributed among the participating states? 8. How are CSBMs perceived from the power perspective of each participating state? 9. How cost effective is implementing the rules in the CSBM agreement? 10. What are the core strengths and weaknesses of the CSBM process, the ways to improve it in the future and the potential threats to the process? 11. What can we learn about this agreement's effectiveness during the current military crisis in Ukraine? 12. To what degree do the effectiveness and modernisation of the Vienna Document's CSBM process depend on the scenarios for European security in the future? 13. Is the 'cyberisation' of the Vienna Document's CSBMs required in the present security environment to maintain the agreement's effectiveness?