If nation state is invaded by another nation, what purpose has its government failed to perform

Protection

Explanation:

A nation state can be described as a state in which majority of the people living share common cultures and beliefs. It is the work of the government to protect the rights of the majority as well as the minority cultures of the nation state. If a government fails to do so or if a nation state is invaded by another nation, then it is the government which is to be held accountable for failing to provide protection to the nation state.