dragon's teeth
Military term for anti-tank obstacles resembling a row of pointed teeth. Also used in mythological contexts.
Dragon's teeth were installed at the border to prevent tank incursions.
In mythology, it is said that sowing dragon's teeth gives birth to warriors.
Compound of 竜 (ryū, 'dragon') + の (no, possessive particle) + 歯 (ha, 'tooth'). The military sense is a calque from English 'dragon's teeth'.