We were guarded by sentries against surprise attack.是什么意思？

We were guarded by sentries against surprise attack.

我们由哨兵守卫,以免遭受突袭.

we

pron. 我们，咱们，笔者，本人，朕，人们；

例句
...expensive make-up that we saw being advertised by a beautiful model...
我们所见的由一位漂亮模特代言的昂贵化妆品

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

guarded

adj. 谨慎的，有保留的；v. 保护，控制( guard的过去式和过去分词 )；

例句
The boy gave him a guarded look...
那个男孩充满戒心地瞧了他一眼。

by

prep. 在…旁边，表示方式，由于，经过；adv. 经过，表示保留或保存时用，短暂拜访；

例句
...expensive make-up that we saw being advertised by a beautiful model...
我们所见的由一位漂亮模特代言的昂贵化妆品

sentries

n. 哨兵，步兵( sentry的名词复数 )；

例句
C Company's sentries were just ahead.
C连的哨兵就在前头。

against

prep. 反对，对…不利，紧靠，以防；

例句
His hand brushed against hers; it could have been either accidental or deliberate.
就在有意无意间，他的手轻轻拂过她的手。

surprise

vt. 使惊奇，突袭，意外发现；n. 惊喜，惊奇，意外的事；

例句
A nasty surprise awaited them in Rosemary Lane.
在罗斯玛丽巷，一起严重的意外事件正等待着他们。

attack

vt.& vi. 攻击，进攻，抨击；n. 攻击，抨击，（队员等的）进攻，（疾病）侵袭；vt. 抨击，非难，侵袭，损害；

例句
The police say they suspect the attack was carried out by animal rights activists.
警方说他们怀疑袭击是由动物权益保护的积极分子们发动的。