彼竭我盈 (Bǐ jié wǒ yíng)

Basic Info

Chinese Idiom: 彼竭我盈 (Bǐ jié wǒ yíng)
Pinyin: bǐ jié wǒ yíng
Literal meaning: “Their [energy] is exhausted; ours is full.”
(彼 = the other side / the enemy; 竭 = exhausted / depleted; 我 = we / our side; 盈 = full / abundant / surging)

The image is of a contest in which the opponent’s strength has run dry while one’s own is at its peak – the perfect moment to strike.

Figurative Definition

It describes a situation in which the opposing side’s morale, energy, or resources have been drained, while one’s own side is still fresh, motivated, and full of fight. It is the strategic condition of relative advantage in momentum: they are spent, you are strong.

It is used in:

Military and competitive strategy – attacking when the enemy is exhausted and your own forces are fresh.
Negotiation and business – gaining advantage when a rival is depleted or demoralized.
Sports – pressing the attack when the opponent is tired and your team is still energetic.

In short: they are running on empty; you are running on full – now is the time to act.

Cultural & Historical Origin

This idiom comes from the Zuo Commentary · Duke Zhuang of Lu, Tenth Year (《左传·庄公十年》), in the famous story of the Battle of Changshao (长勺之战) – the same story that gave us the idiom “一鼓作气” (yī gǔ zuò qì).

The strategist Cao Gui (曹刿) advised the Duke of Lu on how to defeat the invading army of Qi. When the Qi drums sounded for the first attack, Cao Gui held back. He held back again on the second drumbeat. Only on the third did he order the counterattack – and Lu won.

When asked to explain, Cao Gui said:

“夫战，勇气也。一鼓作气，再而衰，三而竭。彼竭我盈，故克之。”

“In battle, what matters is courage. The first drumbeat raises the spirit; the second weakens it; the third exhausts it. Theirs was exhausted and ours was full – that is why we defeated them.”

The phrase “彼竭我盈” was extracted from this explanation. It captures the decisive strategic moment: not merely that the enemy was tired, but that their exhaustion coincided with one’s own peak – the precise condition for victory.

Key Lesson

Timing is a weapon – strike when their strength is gone and yours is full. The idiom teaches patience and timing over raw force: the wise strategist does not attack when the enemy is strongest, nor does he wait until his own side is spent. He waits for the moment of imbalance – 彼竭我盈 – and acts then. It also carries a defensive warning: do not let yourself become the “竭” side – conserve your energy, and never let an opponent attack you when you are exhausted.

Cultural Note

In modern Chinese, “彼竭我盈” is a literary, strategic idiom. It appears in:

Military and historical writing – describing the decisive moment in a campaign.
Sports commentary – when one team is exhausted and the other seizes the initiative.
Business and negotiation – describing a moment of competitive advantage.
Formal and strategic discussion – emphasizing timing and relative strength.

It is closely related to “一鼓作气” (yī gǔ zuò qì – “one drumbeat raises the spirit,” meaning to finish a task in one vigorous push) and “以逸待劳” (yǐ yì dài láo – “to wait at ease for the exhausted enemy”). Together they form a coherent strategic philosophy: conserve your strength, let the enemy spend theirs, and strike at the moment of imbalance.

Its opposite might be “我竭彼盈” – the disastrous reverse situation.

Similar English Expressions

To strike while the iron is hot – Act at the moment of maximum advantage (related but about opportunity, not relative exhaustion).
To catch someone on the ropes – To attack an opponent who is weakened and vulnerable.
They’re running on empty; we’re fresh – A direct descriptive equivalent.
To wait for the enemy to tire, then strike – A strategic paraphrase.
To seize the moment – To act at the decisive instant.
The tide has turned in our favor – The balance of advantage has shifted to us.
To press one’s advantage – To push harder when the opponent is weakening.
To have the upper hand – To hold the advantage (broader).

The closest and most natural equivalents are “to catch someone on the ropes,” “they’re running on empty,” and “to press one’s advantage.”

In short, “彼竭我盈” means their strength is exhausted and ours is full – a strategic Chinese idiom from the Battle of Changshao for the decisive moment of relative advantage, and a timeless reminder that victory often belongs not to the strongest, but to the one who strikes when strength has shifted.