But the Catalans were better strategists than the impetuous Duke of Athens. They knew that the strength of the Franks lay in the rush of their splendid cavalry, and they laid their plans accordingly. The marshy soil of the Copaic basin afforded them an excellent defence against a charge of horsemen; and they carefully prepared the ground by ploughing it up, digging a trench round it, and then irrigating the whole area by means of canals from the river Kephissos. By the middle of March, when the two armies met face to face, a treacherous covering of green grass concealed the quaking bog from the gaze of the Frankish leaders. As if he had some presentiment of his coming death, Walter made his will—a curious document still preserved[86]—and then, on March 15, took up his stand on the hill called the Thourion, still surmounted by a mediæval tower, to survey the field. Before the battle began, the 500 favoured Catalans whom he had retained came to him and told him that they would rather die than fight against their old comrades. The duke bade them do as they pleased; and their defection added a welcome and experienced contingent to the enemy’s forces. When they had gone, the duke, impatient for the fray, placed himself at the head of 200 French knights with golden spurs and charged with a shout across the plain. But, when they reached the fatal spot where the grass was greenest, their horses, heavily weighted with their coats of mail, plunged all unsuspecting into the treacherous morass. Some rolled over with their armoured riders in the mire; others, stuck fast in the stiff bog, stood still, in the picturesque phrase of the Byzantine historian, “like equestrian statues,” powerless to move. The shouts of “Aragon! Aragon!” from the Catalans increased the panic of the horses; showers of arrows hailed upon the helpless Franks; and the Turkish auxiliaries of the Catalans rushed forward and completed the deadly work. So great was the slaughter that only four Frankish nobles are known to have survived that fatal day—Boniface of Verona, Roger Deslaur, the eldest son of the Duke of Naxos, and Jean de Maisy of Eubœa[87]. At one blow the Catalans had destroyed the noble chivalry of Frankish Greece; and the men, whose forefathers had marched with Boniface of Montferrat into Greece a century earlier, lay dead in the fatal Bœotian swamp. Among them was the Duke of Athens, whose head, severed by a Catalan knife, was borne, long afterwards, on a funeral galley to Brindisi and buried in the church of Santa Croce in his Italian county of Lecce.