In the first half of the 13th century, the crusader states were politically resurgent and economically prospering. By 1240, the Kingdom of Jerusalem had been restored nearly to the same borders it had before the Battle of Hattin. It was strengthened, furthermore, by having at its back the Latin Kingdom of Cyprus.
Yet, between 1240 and 1290 the mainland crusader states essentially disintegrated. There were two main factors that contributed to this collapse, one external and one internal. The external factor was the rise of the Mamluks, the internal factor was the failure of the dynasty of Jerusalem.
Let me examine the external factor first: the Mamluks. The Mamluks were not a dynasty, but a cadre of fanatical, orthodox, military leaders willing to sacrifice economic considerations for religious orthodoxy and victory. The Mamluks pursued a ruthless policy of aggression against the crusader states that included routinely breaking truces, breaking the terms of truces, slaughtering of prisoners, and the wanton destruction of economic assets and cultural monuments to render the cities they captured uninhabitable for generations to come. The Mamluks did not pursue wars of conquest in which the hoped to occupy and benefit from the territory they conquered, but conducted wars of annihilation.
(Medieval depiction of Mamluks)
Let me be clear. Many still point to the Battle of La Forbie as the historical turning point in the fortunes of the Second Kingdom of Jerusalem (the Kingdom that emerged after the Third Crusade). This was a two-day battle in which the the military orders and their Ayyubid allies were defeated by their Ayyubid enemies. From that point in time onwards, the crusader states were on the defensive. They shrank and disintegrated until there was nothing left after the fall of Acre in 1291.
Yet La Forbie was only an apparent and not a substantive turning point. First, note, the battle was not a clash between Christians and Muslims, but rather between Ayyubid princes, in which the Franks had the misfortune to back the losing side. Notably, the defeat did not result in the Kingdom of Jerusalem being over-run and destroyed — precisely because the victor was not engaged in jihad.
Thus, decisive as this battle appears in retrospect, it was not the cause of subsequent decline. As long as the Ayyubid princes remained in control of the territories surrounded the crusader states, it was possible to 1) make truces with them, and 2) play them off against one another. The Ayyubids were far too interested in profiting from the trade they had with the crusader states to undertake serious jihad. This is why I say that it was not until the rise of the Mamluks that the crusaders faced opponents set on their destruction and eradication.
Could the crusader states have prevented the rise of the Mamluks? Impossible to answer. King Louis’ crusade seemed to have spurred their rise, but the Ayyubids were becoming increasingly decadent and fragmented, so perhaps the Mamluk reaction would have come eventually any way.
Let’s turn to the internal crisis: the collapse of the dynasty of Jerusalem. From 1100 to 1225, Jerusalem was ruled by kings resident in the kingdom, who viewed the defense of the Holy Land as their raison d’etre. From Godfrey to John of Brienne, these kings had been fighting men devoted to the kingdom they inherited, whether by blood or marriage.
In 1225, that changed. The marriage of the heiress of Jerusalem, Yolanda (sometimes Isabelle II) to the Holy Roman Emperor Frederick II Hohenstaufen, put the crown — and fate — of Jerusalem into the hands of a man who already possessed a vast Empire. As events were to prove, Frederick II never gave more than an tinker’s damn about Jerusalem. He spent less than a year in the kingdom, he ignored its constitution, sought to humiliate and break the local barons, and on his death bed in 1250 tried to alienate it from the legitimate heir. (For details on this see: Sixth Crusade (crusaderkingdoms.com), Frederick II & His Barons (crusaderkingdoms.com); Frederick II and Henry I , (crusaderkingdoms.com), Imperial Siege of Beirut 1231-1232 (crusaderkingdoms.com))
Frederick II’s son Conrad I and his grandson Conrad II were titular “Kings of Jerusalem” but neither ever set foot in the kingdom, had no understanding of its laws, people or problems, and evidently couldn’t have cared less about it.
In 1268, Conradin of Hohenstaufen died without heirs and a succession dispute broke out between King Hugh III of Cyprus and Maria of Antioch. With a mercenary disregard for the well-being of the kingdom, Maria of Antioch sold her claim to Charles d’Anjou, the younger brother of King Louis of France. Charles, like the latter Hohenstaufens, never set foot in the kingdom, he merely sent a ‘baillie,’ who successfully exploited self-interests and personal vanities to undermine the authority of King Hugh. As a result, the latter abandoned the Kingdom of Jerusalem in disgust and returned to Cyprus. By the time Charles d’Anjou died in 1284 enabling Henry II of Cyprus to be recognized and crowned without dispute as King of Jerusalem, the kingdom existed in name only.
In short, between 1225 and 1284, the Kingdom of Jerusalem effectively had no central authority. It is hardly surprising that in the circumstances internal factions formed, and that rivalries led to bloodshed. Not only did the Genoese and Venetians kill each other in the streets of Acre, but at times the Hospitallers and Templars clashed violently as well — not to mention the long baronial revolt against Frederick II.
Could this have been avoided? Well, obviously, the heiress of Jerusalem should never have been married to a European monarch with so little interest in the kingdom — no matter how good the idea seemed at the time. Once the damage had been done, the only alternative was rebellion, i.e. outright rejection of the “legitimate” king in favor of a local man willing to be an effective king. One can well imagine that Jerusalem would have held its own — even against the Mamluks — under a man like Simon de Montfort (who was proposed as regent by the rebel barons, but rejected by Frederick II) or even under Balian of Beirut, backed by Philip de Montfort.
But that was evidently too radical an idea for the legally-minded barons of Outremer. (For more on the Rule of Law in Outremer at this time see: Educated Elite of the Crusader States (crusaderkingdoms.com))