Crusader states
Size and recruitment

All estimates of the size of Frankish and Muslim armies are uncertain; existing accounts indicate that it is probable that the Franks of Outremer raised the largest armies in the Catholic world. As early as 1111, the four crusader states fielded 16,000 troops to launch a joint military campaign against Shaizar. Edessa and Tripoli raised armies numbering 1,000–3,000 troops, Antioch and Jerusalem deployed 4,000–6,000 soldiers. In comparison, William the Conqueror commanded 5,000–7,000 troops at Hastings and 12,000 crusaders fought against the Moors at Las Navas de Tolosa in Iberia. Among the Franks' early enemies, the Fatimids possessed 10,000–12,000 troops, the rulers of Aleppo had 7,000–8,000 soldiers, and the Damascene atabegs commanded 2,000–5,000 troops. The Artuqids could hire as many as 30,000 Turks, but these nomadic warriors were unfit for lengthy sieges. After uniting Egypt, Syria, and much of Iraq, Saladin raised armies around 20,000 strong. Egyptian money and Syrian manpower represented the two critical factors underpinning Saladin's military might during the period. In response, the Franks quickly increased their military force up to around 18,000 troops by 1183, but not without implementing austerity measures. In the 13th century, the control of Acre's lucrative commerce provided the resources to maintain sizeable armies. At La Forbie, 16,000 Frankish warriors perished in the battlefield, but this was the last occasion when a united Jerusalemite army fought a pitched battle. During the 1291 siege of Acre, about 15,000 Frankish troops defended the city against more than 60,000 Mamluk warriors.

The crusader states' military power depended mainly on four major categories of soldiery: vassals, mercenaries, visitors from the west, and troops provided by the military orders. Vassals were expected to perform their military duties in person as fully armed knights, or more lightly armoured serjants. Unmarried female fief holders had to hire mercenaries; their wards represented underage vassals. Disabled men and men over sixty were required to cede their horses and arms to their lords. Vassals who owed the service of more than one soldier had to mobilise their own vassals or employ mercenaries. A feudal lord's army could be sizeable. For example, 60 cavalrymen and 100 footmen accompanied Richard of Salerno, then lord of Marash, during a joint Antiochene–Edessene campaign against Mawdud in 1111. Complaints about Frankish rulers' difficulties in paying off their troops abound, showing the importance of mercenary troops in Levantine warfare. Mercenaries were hired regularly for military campaigns, for garrisoning forts and particularly in Antioch, for serving in the prince's armed retinue. The crusader states could have hardly survived without constant support from the west. Armed pilgrims arriving at moments of crisis could save the day, like those who landed just after Baldwin I's defeat at Ramla in 1102. Westerners were unwilling to accept the Frankish leaders' authority.
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