A nuclear arsenal refers to a country's collection of nuclear weapons and the delivery systems used to deploy them. These weapons are designed to release energy through nuclear reactions, either fission or fusion, and can cause massive destruction. Countries maintain nuclear arsenals for deterrence, ensuring that potential adversaries are discouraged from attacking due to the threat of devastating retaliation. The size and capability of a nuclear arsenal can vary significantly between nations. Major nuclear powers, such as the United States and Russia, possess thousands of warheads, while other countries, like North Korea and India, have smaller stockpiles. International treaties, such as the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), aim to regulate and reduce the proliferation of these weapons.