The commander instructed his soldiers to embattle behind the city walls in preparation for the enemy's attack.

embattle 由前缀 em-（表示"使进入某种状态"）和名词 battle（战斗）组成，字面意思是"使进入战斗状态"，引申为"布阵、设防"的意思。这里指士兵们按照战术要求在城墙后方排列成防御阵型。