Sentence:  What skill and dexterity soldiers, who are called together "only" once a week, may possess, in <WSD>"trouncing</WSD>" an enemy, which has already <WSD>"trounced</WSD>" half Europe, I will not pretend to determine; [...] 
Meaning of the word marked with <WSD> tags:  To beat or overcome thoroughly, to defeat heavily; especially  to win against (someone) by a wide margin.