When cities fell they used to be sacked by the attackers. These days this fortunately isn't nearly as common. When did this shift in treatment of captured cities happen?
If a general definition to sacking is applied, one could argue WWII was the last time it happened on a considerable scale. However, for some reason or another, we stopped referring to such actions as 'sacking' sometime far before, but the general idea was the same: the conquerors loot, plunder, steal from, and (often) rape or murder the people of the captured city.