How has North Korea's nuclear arsenal developed following Russia's invasion of Ukraine?

Following Russia's invasion of Ukraine, North Korea's ballistic missile testing has increased dramatically, with the highest recorded number of tests occurring in 2022-2023. While experts traditionally estimated North Korea's nuclear arsenal at between 50-60 warheads (the smallest of any nuclear state), more recent assessments suggest significant growth. A 2023 study by the Seoul-based Korea Institute for Defense Analyses indicates the actual number may be closer to 80-90 nuclear warheads. This rapid expansion coincides with increased military collaboration with Russia and North Korea's constitutional changes designating South Korea as its primary enemy, potentially shifting the geopolitical balance in Northeast Asia.