Before Sád reached the rendezvous, Mothanna had passed away. Omar entirely approved his having withdrawn from Mesopotamia, to the right bank of the Euphrates, and there rallied the Bedouin tribes along the lower waters skirting the desert.[254] This was all the more necessary, as the court of Persia was then endeavouring to detach the great tribe of the Beni Bekr ibn Wâil by an appeal to their ancient alliance with the house of Hîra. Moänna, brother of Mothanna, had just returned from a mission to this (his own) tribe, and had succeeded in frustrating the attempt. Bearing intelligence of this success, as well as the melancholy tidings of his brother’s death, he went out to meet Sád on his march. He communicated also his brother’s dying message to the new commander, advising that the Arabs should hold to their ground on the confines of the desert. ‘Fight there the enemy’ were the last words of Mothanna;--‘Ye will be the victors; and, even if worsted, ye will still have the friendly and familiar desert wastes behind: there the Persians cannot enter, and from thence ye will again return to the attack.’ Sád, as he received the message, blessed the memory of the great general. He also made the family he had left his special care; and, the more effectually to discharge the trust, as well as to mark his estimate of the man, he, in true Arab fashion, took to wife his widow Selma. [Sidenote: Sád marshals his troops in new order.] The army was marshalled by Sád anew. Companies were formed of ten, each under a selected leader. Warriors of note were appointed to bear the standards. Columns and battalions were made up by clans and tribes; and so by clans and tribes they marched, and also went into the field of battle. Departments also were established for the several services incident to a campaign.[255] The chief commands were all given to veterans, who had fought under the Prophet’s banner; for in this army there were no fewer than 1,400 Companions, and ninety-nine who had fought at Bedr.[256] Following Mothanna’s counsel, which was confirmed by Omar, Sád marched slowly to Odzeib, still on the border of the desert. [Sidenote: Encamps at Câdesîya. A.H. XIV. Summer, A.D. 635.]Leaving the women and children there under protection of a squadron of horse, he advanced to Câdesîya. Here was a great plain washed on its eastern side by the ‘old’ Euphrates,[257] and bounded on the west by the _Khandac_, or Trench of Sapor (in those days a running stream), with the desert beyond. The plain was traversed by a road from the south, which here crossed the river by a bridge of boats leading to Hîra, and onwards across the peninsula to Medâin. Such was the field on which the great battle was to be fought that would settle the fate of Persia. Sád, keeping still to the western bank of the Great River, fixed his head-quarters at Codeis, a small fortress overlooking the stream a little way below the bridge. He had thus the great plain