wǒ jūn / chèn / dí jūn / bù bèi / chéng xū / ér / rù / yī jǔ / qǔ shèng

我军趁敌军不备，乘虚而入，一举取胜。

Our army took advantage of the enemy's unpreparedness, broke in through their weakness, and won in one stroke.