When the Byzantines and Crusaders besieged Nicaea, the Seljuk Turks saw that they were a serious invasion force. Kilij Arslan was fighting another tribe of invading Turks to the east. He had only just declared independence for “Rum,” that is, the former Roman lands of Anatolia, and he had to battle back invading tribes who saw opportunity in chaos. For the remainder of the time that the Europeans were in his territory, the Sultan focused on trying to stop them. He wasn’t able to.
Remember that not long before this, an Ismaili assassin dressed as a dervish asking alms had killed the Grand Vizier on his way from Isfahan to Baghdad. The Grand Vizier was a well-educated Persian who understood governance strategy better than the Turkish Sultans whom he served. Until now, Baghdad had been enough of a central government that an invasion would have provoked a concerted defense. But after one Sultan died with only a child as heir and then the savvy Grand Vizier was murdered, Baghdad lost all control of its provinces. Not only was it no longer in control of North Africa or Egypt; it lost control of Syria and many Persian cities. Many Turkish city governors were at war, attempting to seize more power. So at this exact point in history, the Muslim lands were too fractured and recently-invaded to make a unified defense.
As the Crusaders marched across Anatolia, from Nicaea to the coast near Syria, they broke into two armies: French and Norman. The Normans were about a day’s march ahead of the French when Kilij Arslan brought down his main army to stop them. The Sultan did not realize that the French army was as large as it was, or else he thought it was farther away. As the Normans defended their camp, the vanguard of the French army arrived. Arslan had to withdraw from a battle where he was clearly outnumbered.
The European forces stayed near each other from then on, and he did not attack them. However, Turks went in advance to destroy and burn everything along the road. By the time they reached the coast of the Mediterranean, some of the Crusaders were starving. They lost a lot of horses in the heat.
If the regional Turks could have joined the Sultan of Rum to attack the Crusaders at that time, they might have won easily. But even as the Europeans approached, the Turkish governors of Aleppo, Antioch, Damascus and Jerusalem were allying against each other and preparing to march on each other’s territory. At the center of this drama was a pair of brothers who had turned against each other and were battling for supremacy. Without a powerful central government to force them into unity, they only turned to meet the Europeans as small local armies, city by city.
The bad summer march through burnt farmlands brought the first year of the Crusade to a close. Joint leadership could not last beyond that first year. The Papal Legate could not enforce his nominal leadership, and the four leading French and Norman princes jockeyed for power. None of them was clearly strong enough to take control. As they reached the edges of Bible lands (cities that Paul had visited), one of the Boulogne brothers set off on his own.