The Sacred Band was a group of 300 hand picked soldiers “composed of lovers and beloved” and renowned for their heroism. Plutarch puts it like this:
For men of the same tribe or family little value one another when dangers press; but a band cemented by friendship grounded upon love is never to be broken, and invincible; since the lovers, ashamed to be base in sight of their beloved, and the beloved before their lovers, willingly rush into danger for the relief of one another. Nor can that be wondered at since they have more regard for their absent lovers than for others present; as in the instance of the man who, when his enemy was going to kill him, earnestly requested him to run him through the breast, that his lover might not blush to see him wounded in the back. Plutarch, Life of Pelopidas.
I can see the logic in that.
The Sacred Band was the most feared unit in the Theban army until it was defeated at the battle of Chaeronea by Philip of Macedon, the father of Alexander the Great.
Philip, after the fight, took a view of the slain, and came to the place where the three hundred that fought his phalanx lay dead together, he wondered, and understanding that it was the band of lovers, he shed tears and said, "Perish any man who suspects that these men either did or suffered anything that was base."