以夷制夷

yǐ yí zhì yí

ㄧˇ ㄧˊ ㄓˋ ㄧˊ

Idiom

1to use foreigners to subdue foreigners (idiom); let the barbarians fight it out among themselves (traditional policy of successive dynasties)

2Use Western science and technology to counter imperialist encroachment. (late Qing modernizing slogan)