Complex sentence: All males aged 21 to 30 were required to register for military service for a service period of 12 months; the age limit was later raised in August 1918 to a maximum age of 45.
Split into simpler sentences: All males aged 21 to 30 were required to register for military service for a service period of 12 months. The age limit was later raised in August 1918 to a maximum age of 45.