【不宣而战】〖bù xun-ér zhàn〗[Start an undeclared war; fight without a declaration of war; open hostilities without declaring war]

不择手段霸权酋，

宣威耀武俄乌斗，

而今航母围台海，

战略导弹镇美欧。

不宣布开战，就突然发起进攻。No announce make war, just suddenly launch attack.反：先礼后兵。