The Christians, led by the King, pursue the Muslims along the coast, finally catching their enemies at Mons Gisardi, near Ramla.
The location is disputed, as Ramla is a large region that includes the town under the same name.
Malcolm Barber equates Mons Gisardi with the mound of al-Safiya.
Saladin's chronicler Imad ad-Din al-Isfahani refers to the battle taking place by the mound of Al-Safiya, potentially modern Tell es-Safi near the village of Menehem, not far from Ashkelon, and within the contemporary Ramla province.
Al-Safiya means white and, indeed, the Es-Safi hill is white with the foundations of a Crusader castle recently found at the top, called Blanchegarde.
Ibn Al-Athīr, one of the Arab chroniclers, mentions that Saladin intended to lay siege to a Crusader castle in the area, but Saladin's baggage train had been apparently mired.
There is a small stream north of Tell es-Safi bordering farmland that in November might have been plowed up and muddy enough to hinder the passage of the baggage train.
The Egyptian chroniclers agree that the baggage had been delayed at a river crossing.
Saladin is taken completely by surprise.
His army is in disarray, part has been held up by the mired baggage train while another part of his force has scattered into raiding parties across the countryside.
The horses are tired from the long march.
Some men have to hurry to collect their weapons from the baggage train.
Saladin's army, in a state of panic, scrambles to make battle lines against the enemy.
King Baldwin orders the relic of the True Cross to be raised in front of the troops.
The King, whose teenage body is already ravaged by aggressive leprosy, is helped from his horse and drops to his knees before the cross.
He prays to God for victory and rises to his feet to cheers from his army.
The Jerusalem army attack the hurriedly arranged Muslims, inflicting heavy casualties.
The King, fighting with bandaged hands to cover his terrible wounds and sores, is in the thick of the fighting.
Egyptian effective command is under Saladin's nephew Taqi ad-Din.
Taqi ad-Din apparently attacks while Saladin is putting his Mamluk guard together.
Taqi’s son Ahmad dies in the early fighting.
Saladin's men are quickly overwhelmed.
Saladin himself only avoids capture by escaping, as Ralph de Diceto claims, on a racing camel.
By nightfall, those Egyptians that are with the Sultan have reached Caunetum Esturnellorum near the mound of Tell el Hessy (or Hessi).
This is about twenty-five miles from Ramla.
It is only about seven kilometers from Tell es-Safi (al-Safiya).
King Baldwin's victory is total.
He has utterly destroyed the invasion force and has captured Saladin's baggage train.
Baldwin pursues Saladin until nightfall, and then retires to Ascalon.
Deluged by ten days of heavy rains and suffering the loss of roughly ninety percent of his army, including his personal bodyguard of Mamluks, Saladin flees back to Egypt, harassed by Bedouins along the way.
Only one tenth of his army makes it back to Egypt with him.
