Sentence:  "We know for certain that their army does not consist of more than three thousand men, including all sorts." Sir Henry Percy, on hearing this, was greatly rejoiced, and cried out, "To horse! to horse! for by the faith I owe my God, and to my lord and father, I will seek to recover my pennon, and to <WSD>beat up</WSD> their quarters this night." 
Meaning of the word marked with <WSD> tags:  To attack suddenly; to alarm.