At what age must all men register for the Selective Service?

All men in the United States are required to register for the Selective Service at the age of 18. This requirement is established by federal law and is intended to ensure that the government has the ability to draft men into the military in times of national emergency. Registration allows for a pool of potential recruits who can be called upon if needed.

By mandating registration at 18 years of age, the law recognizes this age as the point at which individuals are considered legal adults and are given the full rights and responsibilities of adulthood, including the right to vote and serve in the military. Failing to register can result in penalties, including fines and possible restrictions on receiving federal benefits.

The other age options listed do not align with the legal requirements for registration. 16 and 21 represent different phases of accountability but do not correspond to the Selective Service requirements. 25 also exceeds the age at which registration is mandated.