about 'had P.P'

I don't know why 'had p.p' is being used in the sentence below.
Can you tell me the usage of 'had p.p'?

(1) Robert the Bruce (had swept) aside the web when he (had entered) the cave
(2)The spider (had saved) Bruce’s life, and its persistence (had also impressed) him.
(3)The freedom of the Scottish people (had been won).

The following is the full text.

Robert the Bruce led the Scottish in defending their country against the English, and then later became the first king of Scotland. But for many years, the situation seemed hopeless, as the English attacked Scotland again and again, and won many battles.
One day, Robert the Bruce hid in a small cave after losing a battle. He felt exhausted and hopeless.He wondered if he should give up his struggle and flee to France.
Then he noticed something interesting: a tiny spider was slowly rebuilding its web. Robert the Bruce had swept aside the web when he had entered the cave. A farmer later brought him some food,
breaking the web again. Just after the man left, the spider rebuilt the web one more time.
The next day, English soldiers were searching for Bruce near the cave. Robert the Bruce picked up his sword, expecting a fight. However, a soldier looked into the cave, and called out that nobody could be hiding there because a spider’s web blocked the entrance.
The spider had saved Bruce’s life, and its persistence had also impressed him. According to legend, when the soldiers left, Robert the Bruce lifted up his sword and made a vow: “If at first you don’t succeed — try, try again.”
Bruce regained his strength and renewed his struggle. The Battle of Bannockburn was a turning point, and the Scottish troops defeated the huge English army. The battle lasted for two days, and at the end the English king fled back to England. The freedom of the Scottish people had been won.