Siege of Zaragoza. When Charles reached the outskirts of Zaragoza, he found the situation had changed. Al-Husain, the city's ruler, rejected Suleiman ibn al-Arabi's commitments to the Frankish king, shut himself in Zaragoza, and prepared to defend it at all costs. Charlemagne was forced to undertake a siege of the city, which lasted for days and days, and became slow and desperate. Weeks passed, and the siege made no progress. The defense was heroic. According to Frankish chroniclers, when Charles found himself in this difficult situation, a messenger from Aachen arrived with the terrible news that the Saxons, in revolt, had destroyed the Frankish garrisons in that area. But there are other, more objective chroniclers who claim that it was in Auxerre where he received such news: Ad Autisiodorum civitatem: in the city of Auxerre (Annales Regii). Whether because of this news or because he felt deceived and cheated by the Muslim leaders, the truth is that he now finds himself on this side of the Pyrenees with no one he can trust. Ibn al-Arabi and Abu Thawr become suspects, and the Basques are also inflamed by the recent military interventions against their duke. A wealthy and indignant Charles orders the siege to be lifted. Charles prepares to return to France. But how? He accuses the Muslim kings of not having fulfilled the commitments made to him at Paderborn and demands monetary compensation and a guarantee in the form of ages. Among them, he takes none other than Suleiman ibn al-Arabi himself, who ruled the cities of Barcelona and Girona. The Metz analyst writes that once Zaragoza was besieged, the terrified Saracens gave them ages and a huge amount of gold. The decision to abandon it, comments Abadal, meant acknowledging the political failure of the enterprise. It is fair to think that it was motivated by more complex causes than Zaragoza's mere military resistance to opening the city gates. It is true that in the military art of the time, the violent assault of a fortified city was an undertaking, although not insurmountable, but very costly and difficult. Common practice consisted of negotiated surrenders or those obtained through internal collaboration within the city. It is likely that Charlemagne had attempted the first solution based on negotiations that must have failed (Colloquies..., p. 56). The Frankish army had been out of France for four months. Easter 778 was in mid-April and Charles spent it with his wife at Chasseneuil. The return journey took place in mid-August of the same year. Calculating the marches at 25 km per day, how long did the siege of Saragossa last?