Bǎ értóng dāng réndùn shì yánzhòng de zhànzhēng zuì.
Using children as human shields is a serious war crime.
Tips
memory
人 'person' + 盾 'shield' = a person used as a shield. Direct calque of the English term. The same 盾 appears in 矛盾 (máodùn, 'contradiction' — literally 'spear and shield').