The battalion went directly to the airport to begin digging in.
2
步兵一拿下敌军阵地,立即掘壕固守。
As soon as they had seized the enemy position, the infantry dug themselves in.
3
当防守方的优势火力迫使敌方广泛“掘壕”,以牺牲机动性来获得防护力时,就会发生堑壕战。
Trench warfare is resorted to when the superior firepower of the defense compels the opposing forces to "dig in" so extensively as to sacrifice their mobility in order to gain protection.