Accordingly, when the Midianites, as we have related above, ruled over them, they turned to the Lord, imploring his wonted tender mercy, and obtained it. There was then among the Hebrews one Gideon by name, a righteous man who was dear and acceptable to God. The angel stood by him as he was returning home from the harvest-field, and said unto him, “The Lord is with you, you mighty man of valor.” But he in a humble voice complained that the Lord was not with him, because captivity pressed sore upon his people, and he remembered with tears the miracles wrought by the Lord, who had brought them out of the land of Egypt.
Then the angel said, “Go, in this spirit in which you have spoken, and deliver the people from captivity.” But he declared that he could not, with his feeble strength, since he was a man of very small importance, undertake such a heavy task. The angel, however, persisted in urging him not to doubt that those things could be done which the Lord said. So then, having offered sacrifice, and overthrown the altar which the Midianites had consecrated to the image of Baal, he went to his own people, and pitched his camp near the camp of the enemy.
But the nation of the Amalekites had also joined themselves to the Midianites, while Gideon had not gathered more than an army of thirty-two thousand men. But before the battle began, God said to him that this was a larger number than he wished him to lead forth to the conflict; that, if he did make use of so many, the Hebrews would, in accordance with their usual wickedness ascribe the result of the fight, not to God, but to their own bravery; he should therefore furnish an opportunity of leaving to those who desired to do so.
When this was made known to the people, twenty and two thousand left the camp. But of the ten thousand who had remained, Gideon, as instructed by God, did not retain more than three hundred: the rest he dismissed from the field. Thus, entering the camp of the enemy in the middle watch of the night, and having ordered all his men to sound their trumpets, he caused great terror to the enemy; and no one had courage to resist; but they made off in a disgraceful flight wherever they could.
The Hebrews, however, meeting them in every direction, cut the fugitives to pieces. Gideon pursued the kings beyond Jordan, and having captured them, gave them over to death. In that battle, a hundred and twenty thousand of the enemy are said to have been slain, and fifteen thousand captured. Then, by universal consent, a proposal was made to Gideon that he should be king of the people. But he rejected this proposal, and preferred rather to live on equal terms with his fellow citizens than to be their ruler. Having, therefore, escaped from their captivity, which had pressed upon the people for seven years, they now enjoyed peace for a period of forty years.
Source: Sacred History (New Advent)