The siege of Darum (Mid December 1170) was part of Saladin's first major offensive against the Crusader Kingdom of Jerusalem, and was abandoned after a relief army appeared on the scene.
Early in 1169 Saladin had become vizier of Egypt and command in chief of her armies, following on from his uncle. That winter the Crusaders, with Byzantine allies, attempted to besiege Damietta (25 October-19 December 1169), but the siege failed and the Franks withdrew.
Late in 1170 Saladin launched his own offensive. His first target was the Templar fortress of Darum. This was defended by a garrison commanded by Ansel de Pass, and was a fairly small fort with a nearby suburb.
Saladin's siege would be short-lived, starting on 10 December 1170. He had one heavy stone thrower with his army, which was used to bombard the fort, while his sappers undermined the walls of the suburb. King Amalric responded by raising an army of 250 knights and 2,000 foot. When this army approached Darum, Saladin dismantled his siege engine and moved away. His army sacked Gaza, but couldn't take the citadel, then withdrew. This wasn't the end of Saladin's activities for the year. His main target was probably Ayla (al-Aqaba), a key port at the head of the Gulf of Aqaba. This was held by the Crusaders, and obstructed the pilgrimage route from Egypt to Mecca. Saladin constructed a fleet of pre-packed boats, had then carried across the desert by camels and reassembled in the Red Sea. His main army then joined the fleet, and Ayla was captured on 31 December 1170.
One novel feature of this episode was that it was one of the first times when the Crusader army decided to avoid a direct clash with a Muslim army. Amalric's men moved into Darum while Saladin was sacking Gaza, and didn't intercept him as he withdrew.