He joined the military when he was young.
soldier; rank-and-file soldier
Commonly used for an individual soldier, especially an enlisted one rather than an officer. Can be used in everyday speech.
The soldier was carrying a heavy pack.
My grandfather went off to be a soldier when he was young.
The government sent troops to the border.
The new employee is always working like the boss's errand boy.
He became a soldier at the age of 18.
tin soldier