坚守阵地: hold fast to one's positionstand one's groundstand your groundstand/ hold one's ground
堡垒: fort; fortress; bastion; blockhouse; stronghold 短语和例子封建堡垒 a stronghold of feudalism; 堡垒是最容易从内部攻破的。 the easiest way to capture a fortress is from within.; 堡垒战 blockhouse warfare