The Russo–Ukrainian war has lasted longer than expected due to a combination of two reasons: security threats and military-strategic conflicts. It turned out that through this conflict, the paradigm of war has changed rapidly enough to be called a game changer. This article aims to provide a theoretical analysis of the main factors in Russia's foreign policy that concern a security threat to the instability of the geopolitical buffer zone and Greater Eurasian military strategy, including the leadership of Putinism 4.0, which influenced the Russian invasion of Ukraine. It examines the development aspects and implications of special military Operation Z, which is regarded as Russia's defense military strategy against conflicts with NATO's eastward expansion and Eurasian pluralism. The analysis found that Russia's military strategy and foreign policy will be preemptive and proactive in seeking international security and global order, but at times, however, they show defensive and reactive characteristics. As examined, external factors such as security threats to the identity of a great power in Eurasia, instability in the buffer zone, fear of encirclement on the border, and historical and ethnic factors are expected to serve as constant variables in the decision-making process of Russia's military strategy and foreign policy.