A relief army had the task of relieving or freeing a Siege, besieged city, town, fortress or castle.
Often relief had to be sought by sending a messenger out through the siege lines to deliver a request for help from allies or friendly forces. Well-known examples include:
* Gallic Wars, see Julius Caesar, Caesar ''de bello Gallico'' and Vercingetorix, 52 B. C. or the Battle of Alesia
* Siege of Paris (885–86)
* Fall of Constantinople – here the relieving fleet arrived too late.
* Second Turkish Siege of Vienna (1683)
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Military terminology