In what type of government does the head of state serve a fixed term? In a(n)
system, the head of state serves a fixed term.

A head of state is the public persona who officially embodies a state in its unity and legitimacy. Depending on the country's form of government and separation of powers, the head of state may be a ceremonial figurehead or concurrently the head of government and more.

which time period is this? or is this story fictional, i'm going to need more info to answer this question

they thoght they were going to nuke each other