Poland and the US share a rather complex relations throughout the international modern history; forasmuch as the end of the Great War, the Warsaw Pact, the Cold War to today's bilateral relations. Along with the democratic reforms that emerged in Poland in 1989, the relations between two states have gradually become more than just a close-packed ally in securing each other's geopolitical interests from external threats, specifically in Central Europe. This research is aimed to understand the rationale of the strategic alliance, the modern defense strategic relations between the two will be further examined in this article by employing the realism theory of International Relations; including the conceptual analysis within security dilemma and US-Poland defense collaboration in boosting their dominance, presence, and threats deterrence in the anarchic international system. The research indicates that geopolitical factors, namely the importance of the regional agenda of Central Europe plays a key-role in determining the defense relations among Poland and the US. The political silhouette of the "Iron Curtain" and US outlook on the region have helped the framework of the defense relations; mainly Poland's role in NATO, the enhancement of the joint-military deterrence, bilateral political ties as well as defense strategic adjustment between the two nations.