When the snipe and the clam grapple, the fisherman profits -- It's the third party that benefits from the tussle

During the Warring States Period (475-221BC), the State of Zhao was going to assault the State of Yan. The envoy named Su Dai of the Yan State came to see the King of Zhao. Su Dai told the King the following story:

On my way here I was crossing the Yishui River when I saw a clam just swimming to the bank and opened its shell in the sun, enjoying the sunshine. A snipe flew over and saw a piece of red meat on the ground, so it dived to the ground and pecked at the clam. Before the snipe drew back its beak, it was gripped tightly inside because the clam suddenly felt a sharp pain and closed its shell quickly. The snipe shook its head violently to cast off the clam, but it failed no matter how hard it tried.

The snipe said angrily, "Listen, you clam, it's not going to rain today, and neither will it tomorrow. Then you'll die from thirst. So quick! Let me off!"

The clam was angry too, "You listen, I won't let you off today, and I won't let you off tomorrow, either. Then you'll die of hunger. Do you still dare to eat me?"

The snipe and clam were locked in fight and quarreled, and neither of them wanted to give in first. Just at that moment, an old fisherman came. He picked them up and took both of them home for dinner.

Su Dai then addressed the King of Zhao, Now that Zhao is ready to attack Yan. But, if both states were locked in a long stalemate with neither side ready to yield, then both peoples will be equally worn out. I'm afraid then the powerful Qin State will turn up as the fisherman. Therefore, I do hope that Your Majesty will give this matter careful consideration before you act.

Well said, nodded King of the Zhao. And sure, he gave up his military plan.

From the story comes the idiom . It tells us that the third party will have an advantage fall into his lap when the other two parties are locked in combat for their own personal interests.