During the late Warring States period, the seven great powers clashed in endless wars for supremacy, and the constant fighting between Zhao and Yan brought immense suffering to the people. One year, King Hui of Zhao prepared to attack Yan again. Hearing this, the strategist Su Dai went to see the king to dissuade him. Su Dai said, "Your Majesty, let me tell you a story. As I was traveling here, I saw a clam basking in the sun by the river. A sandpiper swooped down to peck its flesh, but the clam snapped shut, trapping the bird's beak. The sandpiper threatened, 'If it doesn't rain today or tomorrow, you'll be a dead clam!' The clam retorted, 'If I don't let go today or tomorrow, you'll be a dead bird!' Neither would yield, until a fisherman came along and caught them both. Now, Zhao and Yan are locked in a similar standoff. While you fight, the powerful state of Qin waits like that fisherman. If you attack Yan, you will only weaken both our kingdoms and hand Qin the victory." King Hui of Zhao was convinced and called off the invasion. This story gave rise to the idiom "the sandpiper and the clam locked in a stalemate," reminding us that when two parties refuse to compromise, a third party often reaps the rewards.
Su Dai first told King Hui of Zhao an interesting fable:
On a bright, sunny day, a clam opened its shell to bask on the riverbank. A sandpiper spotted it from above and, delighted, swooped down to thrust its beak into the clam's flesh. The clam quickly snapped its shell shut, clamping down firmly on the sandpiper's beak.
The snipe, straining with all its might but still unable to pull its beak free, threatened the clam, "Just you wait if you don't let go. No rain today, no rain tomorrow—without water, you'll dry up and die on this riverbank!"
The sandpiper and the clam held fast to each other, neither willing to let go. Just as both were utterly exhausted, a fisherman happened by. Seeing a plump river clam and a beautiful sandpiper locked in a death grip, unable to move, he grinned with delight and, without any effort, scooped them both up together.
After telling this story, Su Dai advised King Hui of Zhao, "Zhao and Yan are evenly matched. If Zhao attacks Yan, both sides will be locked in a prolonged stalemate. Then, powerful Qin will profit like the fisherman. I urge Your Majesty to think thrice before acting."
King Zhao Hui of Zhao found Su Dai's reasoning so compelling that he immediately called off the planned invasion of Yan.
Later, based on Su Dai's fable, people summarized it as "Snipe and Clam Locked in Combat" (sometimes adding "Fisherman Gains the Profit"), also called "Snipe and Clam Struggle, Fisherman Gains," a metaphor for both sides locked in conflict, both losing, while a third party profits.
Source: *Strategies of the Warring States*, Chapter "Strategy of Yan II"
Meaning of the Idiom: Later, the Chinese idiom "鹬蚌相持" came to describe when two parties refuse to compromise, a third party often reaps the rewards.