What term refers to a military group that takes control over a country?

The term that refers to a military group taking control over a country is "junta." A junta typically consists of military leaders who come to power, often through a coup d'état, in which they overthrow the existing government. This type of leadership is characterized by a concentration of power in the hands of the military, often resulting in authoritarian rule.

In contrast, an oligarchy refers to a form of power held by a small group of individuals, usually distinguished by wealth or noble birth. Democracy, meanwhile, is a system of government in which power is vested in the people, who exercise that power directly or through elected representatives. Plutocracy is a government or control by the wealthy, where power rests in the hands of the affluent class. Each of these terms describes different forms of governance or power structures, making "junta" the appropriate choice in the context of a military takeover.