The attack was sudden and fierce.

The Flemings, who, knowing the smallness of his force, had made no preparations to repel an attack, were seized with a panic at the fierce appearance and the wild cries of the Welsh, who fell upon them with such fury that two hundred of the Flemings were slain, and the Welsh cut their way through the beleaguering line.
The news of this feat was received with immense enthusiasm, throughout the principality.

Great numbers flocked to Glendower's standard; the bards sung songs of his victory, at every village in Wales; and so formidable did his position become that the Lords of the Marches wrote to the king, saying that the matter had gone altogether beyond them, and that his presence, with an army, was urgently needed.
Even in Ludlow, extra sentries were placed upon the walls, the garrison was kept in a constant state of vigilance, and mounted men were stationed, miles out, to bring in the news of the approach of any hostile force.
"'Tis a thousand pities," Sir Edmund said, when the news of the defeat of the Flemings reached him, "that these fellows did not send news to me, a day or two before they undertook this business; for in that case I would have myself headed a force of a couple of hundred of my best men-at-arms, and joined them at some spot in the mountains; and had we been there, you may be sure that Glendower would never have fought his way out.

The Flemings are doubtless stout fighters, as they have proved over and over again, in their own country; but they are all unused to mountain warfare, or to fight with wild men, and were doubtless scared by the shrill cries with which the Welsh always advance to battle.
Doubtless, too, these men Glendower keeps with him are his best fighters, and they knew that, if they did not succeed in making their way out, no mercy would be shown to them, seeing that they have shown none themselves.

Had the battle been on a plain, I doubt not that the Flemings would have stood against many times the number of Welshmen that Owen had with him; but this hill warfare was altogether strange to them, and of course they had not the habit of quickly rallying, and meeting the attack, that is second nature with our men-at-arms.