1.fierce a. 凶猛的,残忍的;狂热的,强烈的

例句：The postman was bitten by a fierce dog.
      那个邮递员被一只恶狗咬了。

      The country was torn apart by fierce tribal hostilities.
      那个国家被部落间的激烈冲突弄得四分五裂。

2.dusty a. 灰尘多的,无聊的,含糊的,粉末状的

例句：Sunlight filtered in through the dusty window.
      阳光从满是灰尘的窗子透进去。

3.retreat n. 休息寓所,撤退,隐居,退避,避难所

例句：A brave retreat is a brave exploit.
      勇敢的退却也是勇敢的行为。

      Suddenly they found their retreat cut off.
      他们突然发现退路已被切断。

1.But they did want to prevent him from reaching Beauregard.

prevent sb from doing sth,相当于stop sb from doing，都是防止某人做某事，记住from后面的动词一定要用动名词形式。

2.He stopped moving forward and prepared to defend against what seemed to be a strong Confederate attack.

what在这里引导宾语从句，是介词against的宾语。

3.But the battleground was covered so thickly with trees that the crowds saw little of the fighting.

so……that 引导结果状语从句。