Every city and town within this state is hereby authorized to continue on its payroll, either at full or partial pay, all or any of its regular officers and employees who are called into or enlist in the military or naval service of the United States, and to make such provisions as the city or town shall see fit to hold the positions thus vacated for these officers and employees at the expiration of their military or naval service, and to employ temporary assistants to perform the duties of these absent officers and employees.