What age were soldiers in Word War I?

While the official ages to serve in all of the countries in World War 1 ranged from about 17-45 years old, records indicate that some soldiers serving in the British army were as young as 12 years old.

Before the prominence of birth certificates, it was easy to lie about one's age, especially if the boys looked older than they actually were. In the case of the British Empire, recruitment officers were actually paid per enlistment, so they were more than happy to look the other way and recruit extremely young men, in order to get paid more. The Germans on the other hand, made any citizen a possible soldier if they were between the ages of 17 and 45.