Requiring citizens to serve in the military during times of war is an example of which function of government?

The correct answer to this open question is the following.

Requiring citizens to serve in the military during times of war is an example of the function of government that is to protect the American citizens in dangerous times.

That is why the United States government recruited young men to the army in World War 1 and World War 2. It was called the draft. Although it was mandatory, since 1973, the draft is voluntary but young Americans have to register in the Selective Service System. The United States Congress has the power to reinstate the mandatory draft in the extreme case the United States faces some threat.

the social contract theory

straight down to hell mate