During the early-to-mid-1960s the Nike Ajax batteries were upgraded to the Hercules system. The new missiles had greater range and destructive power, so about half as many batteries provided the same defensive capability. Regular Army batteries were either upgraded to the Hercules system or decommissioned. Army National Guard units continued to use the Ajax system until 1964, when they too upgraded to Hercules. Eventually, the Regular Army units were replaced by the National Guard as a cost-saving measure, since the Guard units could return to their homes when off duty.