Open city

In war, an open city is a settlement which has announced it has abandoned all defensive efforts, generally in the event of the imminent capture of the city to avoid destruction. Once a city has declared itself open, the opposing military will be expected under international law to peacefully occupy the city rather than destroy it.

The concept of an open city emerged during World War I, where cities were declared demilitarized in an attempt to avoid destruction. Protocol I of the Geneva Conventions forbids the attacking party to "attack, by any means whatsoever, non-defended localities". The intent is to protect the city's civilians and cultural landmarks from a battle which may be futile.

Attacking forces do not always respect the declaration of an open city. Defensive forces will occasionally use the designation as a political tactic as well. In some cases, the declaration of a city to be open is made by a side on the verge of surrender and defeat; in other cases, those making such a declaration are willing and able to fight on, but prefer that the specific city be spared. Often, resistance movements will be active in open cities, straining the temperate conduct of the occupying forces.