The characters combine to paint a vivid, literal picture: [背] turning your back [水] to the water for [一] one final [战] battle. This simple image powerfully conveys the core concept of having no escape route, forcing a final, all-out effort.
The idiom comes from one of China's most famous military tales, the Battle of Jingxing (井陉之战) in 204 BCE, recorded in Sima Qian's *Records of the Grand Historian*. The brilliant general Han Xin (韩信) was leading a small army of about 10,000 men against a massive, 200,000-strong Zhao force. In a move that defied all conventional military wisdom, Han Xin positioned his troops with their backs directly against a river. His own commanders were horrified, as basic tactics dictate leaving an escape route to prevent panic. But Han Xin knew exactly what he was doing. He explained later that by placing his soldiers in a “death ground” (死地), they would have no choice but to fight with superhuman ferocity, as retreat meant certain death by drowning. His strategy worked perfectly. The soldiers, knowing there was no escape, fought with incredible valor and achieved a stunning victory. From this story, the principle 置之死地而后生 (zhì zhī sǐ dì ér hòu shēng)—“to place oneself in a death ground and then be reborn”—was established, with `背水一战` as its most famous expression. Comparison to a Western Concept: This is very similar to the English phrases “to burn one's bridges” or “to cross the Rubicon.” All three refer to committing to a course of action from which there is no return. The key difference lies in the focus. “Burning one's bridges” emphasizes the *decision* to make retreat impossible. `背水一战` focuses on the *state of mind during the ensuing conflict*. It's about the psychological power unleashed by that irreversible decision. It carries a heroic and strategic connotation, suggesting that this desperate situation was engineered for the specific purpose of winning.
`背水一战` is a formal and powerful idiom used to describe situations with extremely high stakes. It's common in formal speeches, news reports, and serious discussions.
The connotation is almost always positive and heroic. It evokes admiration for the courage, determination, and willingness to risk everything for a single, crucial goal.