What event has caused the Caucasus region to become so troubled since the 1990s is?

The Caucasus region has been troubled since the 1990s primarily due to the collapse of the Soviet Union, which led to a power vacuum and the emergence of ethnic conflicts. This resulted in violent struggles for independence and territorial disputes, particularly in areas like Chechnya, Nagorno-Karabakh, and Abkhazia. Additionally, geopolitical interests from neighboring powers have further complicated the situation, exacerbating tensions and leading to prolonged instability. The legacy of these conflicts continues to impact the region's security and political landscape.