The Lion and the Three Bulls (Greek Folk Tale)

Three Bulls were grazing in a meadow, and were watched by a Lion, who longed to capture and devour them, but who felt that he was no match for the three so long as they kept together. So he began by false whispers and malicious hints to foment jealousies and distrust among them. This stratagem succeeded so well that ere long the Bulls grew cold and unfriendly, and finally avoided each other and fed each one by himself apart. No sooner did the Lion see this than he fell upon them one by one and killed them in turn.

The quarrels of friends are the opportunities of foes.