The purpose of a nation’s boundaries to prevent other countries from invading territory
Explanation:
Borders are defined to limit the other countries from invading another country's space. They mark the farthest limit up to which a country possesses sovereignty, inside of which no other country has any power of its own. Each country can enforce rules only within their boundaries and nowhere else. There are certain rules of each border one must follow if they have to cross it. This will ensure the countries from being invaded by each other and also provides protection against terrorists, immigrants and also smuggled goods.