Sentence:  What this attack represents is more powerful than the attack sequence itself, which is a double-edged sword, but let's start with the positive. If what we see is any indication, Euron has <WSD>decimated</WSD> Yara's fleet and cut it off before it was able to fetch the Dornish army. 
Meaning of the word marked with <WSD> tags:  To devastate: to reduce or destroy significantly but not completely.