Guards

From HELP 10.7 CITY GUARDS

The Minister of Security and his or her aides in each city have the power to protect the city from enemies, by declaring people official enemies of the city, and by purchasing a variety of guards to both guard specific locations within the city, and patrol it looking for enemies generally.

If you're being attacked within your city and need help, you'll want to CALL FOR HELP. Doing so will attract the interest of city guards within shouting range, who will come running to help. But be warned that CALL FOR HELP takes equilibrium, and that the guards will -only- attack city enemies. Guards will also act to protect other NPC citizens of your city, coming at their call when these poor civilians are attacked.