when the enemy is defeated, the victorious soldiers can be killed off
A yojijukugo originating from the longer phrase 狡兎死して良狗烹らる, meaning that once a cunning rabbit is caught, the hunting dog is no longer needed and may be cooked. Used metaphorically to describe how those who have served their purpose are discarded or eliminated.
See also: 狡兎死して走狗烹らる
The phrase 狡兎良狗 comes from 狡兎死して良狗烹らる.
The full classical phrase from which 狡兎良狗 is abbreviated; more explicit and even rarer in modern usage.
Abbreviated from the classical Chinese-derived phrase 狡兎死して良狗烹らる (when the cunning rabbit dies, the good dog is cooked). The exact historical derivation is uncertain, but it reflects a well-known parable about the fate of those who outlive their usefulness.