desert battles

[Randarkmaan]

I don't think the heat penalties will be the same as what they were in MTW.
Anyway Islamic warriors were not as lightly armed our armoured as many often assume... Arab cavalrymen (not bedouin) for instance wore long mail hauberks, iron helmets (often with coifs or aventails), wielded lances and swords (straight up to the end of the 12th century, then the Arabs also started using sabres on a large scale) and carried shields (many of which were of kite construction). If you compare this to the equipment of a European cavalrymen up until the 13th century you will realize how strikingly similarily they are equipped. Farther east (in Persia and Trasnoxania) equipment was usually heavier than this and often included a horse with iron barding (lamellar or mail)

EDIT: Oh, seems like the above poster said exactly what I did...

I think the biggest things that held the europeans back was poor knowledge of the area, atrociously bad logistics, being massively outnumbered, and the ridiculous infighting and bickering that their multinational groups engaged in at any opportunity.

Their heavily armored knights were an asset, and would routinely smash vastly larger arab formations if the latter would stand still like obliging fellows and let themselves get charged.

The Crusaders weren't always massively outnumbered, though towards the end they were because the enthusiasm for Crusades had dropped in Europe and Europeans were far too busy killing each other (as most people in the world have been preoccupied with since the beginning of time). The sad thing (for the Crusader states) was that often when troops from Europe came they just raided some territory sieged a castle and went home whilst the Crusader States had to fight a war. Another thing that many do not know is that at Hattin Saladin used mostly only his 12,000 professional cavalrymen (who were mostly light cavalry, though about 4-5000 were heavy cavalry, the Crusaders numbered about 22 000 men of which about 5000 were heavy cavalry) the rest of his force (his infantry), which was mostly made up of volunteers were 'preserved' for siege warfare, though some were used at the end of the battle and some lit bonfires amongst the Crusaders while they were sleeping.

Anyway a charge by heavy cavalry, against a foe that is standing still and not braced properly for the attack (lacking spears, pikes, ditches... etc) will most of the time ride the opposition down, you must not forget that this happened with heavy cavalry charges against European armies as well. Also the Muslims used their heavy cavalry in a bit different way from the Europeans, their heavy cavalry usually covered the withdrawal of light harrasing cavalry (Ayyubids and other Turkish influenced armies), executed repeated charge and withdrawal attacks with a portion of their horsemen (nearly all, but not so much from the Turks), or used their heavy horsemen to cover an infantry advance (Fatimids and earlier Muslim armies), most of these tactics were similar to the ones used by the Byzantines. In pitched battles European heavy cavalry mostly relied on an all out charge with nearly everything they had, they lacked proper battlefield communications to use other tactics, this type of attack was terminal to the enemy if it succeded but it was very risky and if stopped often spelled certain disaster for the whole army. Also by the 13th century Mamluks were able to effectively halt a charge by Crusader heavy cavalry using horse-archery alone (not skirmishing mind you, horse-archers drawn up in ranks firing while standing still).