The false or genuine magnanimity of Mahmud the Gaznevide was not imitated by Alp Arslan; and he attacked without scruple the Greek empress Eudocia and her children. His alarming progress compelled her to give herself and her sceptre to the hand of a soldier; and Romanus Diogenes was invested with the Imperial purple. His patriotism, and perhaps his pride, urged him from Constantinople within two months after his accession; and the next campaign he most scandalously took the field during the holy festival of Easter. In the palace, Diogenes was no more than the husband of Eudocia: in the camp, he was the emperor of the Romans, and he sustained that character with feeble resources and invincible courage. By his spirit and success the soldiers were taught to act, the subjects to hope, and the enemies to fear. The Turks had penetrated into the heart of Phrygia; but the sultan himself had resigned to his emirs the prosecution of the war; and their numerous detachments were scattered over Asia in the security of conquest. Laden with spoil, and careless of discipline, they were separately surprised and defeated by the Greeks: the activity of the emperor seemed to multiply his presence: and while they heard of his expedition to Antioch, the enemy felt his sword on the hills of Trebizond. In three laborious campaigns, the Turks were driven beyond the Euphrates; in the fourth and last, Romanus undertook the deliverance of Armenia. The desolation of the land obliged him to transport a supply of two months' provisions; and he marched forwards to the siege of Malazkerd, an important fortress in the midway between the modern cities of Arzeroum and Van. His army amounted, at the least, to one hundred thousand men. The troops of Constantinople were reënforced by the disorderly multitudes of Phrygia and Cappadocia; but the real strength was composed of the subjects and allies of Europe, the legions of Macedonia, and the squadrons of Bulgaria; the Uzi, a Moldavian horde, who were themselves of the Turkish race; and, above all, the mercenary and adventurous bands of French and Normans. Their lances were commanded by the valiant Ursel of Baliol, the kinsman or father of the Scottish kings, and were allowed to excel in the exercise of arms, or, according to the Greek style, in the practice of the Pyrrhic dance.

On the report of this bold invasion, which threatened his hereditary dominions, Alp Arslan flew to the scene of action at the head of forty thousand horse. His rapid and skilful evolutions distressed and dismayed the superior numbers of the Greeks; and in the defeat of Basilacius, one of their principal generals, he displayed the first example of his valor and clemency. The imprudence of the emperor had separated his forces after the reduction of Malazkerd. It was in vain that he attempted to recall the mercenary Franks: they refused to obey his summons; he disdained to await their return: the desertion of the Uzi filled his mind with anxiety and suspicion; and against the most salutary advice he rushed forwards to speedy and decisive action. Had he listened to the fair proposals of the sultan, Romanus might have secured a retreat, perhaps a peace; but in these overtures he supposed the fear or weakness of the enemy, and his answer was conceived in the tone of insult and defiance. "If the Barbarian wishes for peace, let him evacuate the ground which he occupies for the encampment of the Romans, and surrender his city and palace of Rei as a pledge of his sincerity." Alp Arslan smiled at the vanity of the demand, but he wept the death of so many faithful Moslems; and, after a devout prayer, proclaimed a free permission to all who were desirous of retiring from the field. With his own hands he tied up his horse's tail, exchanged his bow and arrows for a mace and cimeter, clothed himself in a white garment, perfumed his body with musk, and declared that if he were vanquished, that spot should be the place of his burial. The sultan himself had affected to cast away his missile weapons: but his hopes of victory were placed in the arrows of the Turkish cavalry, whose squadrons were loosely distributed in the form of a crescent. Instead of the successive lines and reserves of the Grecian tactics, Romulus led his army in a single and solid phalanx, and pressed with vigor and impatience the artful and yielding resistance of the Barbarians. In this desultory and fruitless combat he spent the greater part of a summer's day, till prudence and fatigue compelled him to return to his camp. But a retreat is always perilous in the face of an active foe; and no sooner had the standard been turned to the rear than the phalanx was broken by the base cowardice, or the baser jealousy, of Andronicus, a rival prince, who disgraced his birth and the purple of the Cæsars. The Turkish squadrons poured a cloud of arrows on this moment of confusion and lassitude; and the horns of their formidable crescent were closed in the rear of the Greeks. In the destruction of the army and pillage of the camp, it would be needless to mention the number of the slain or captives. The Byzantine writers deplore the loss of an inestimable pearl: they forgot to mention, that in this fatal day the Asiatic provinces of Rome were irretrievably sacrificed.