Possibly in all human affairs we should regulate all our actions by opportunity, for opportunity is more powerful than anything else; and this is especially true in war,
for there it is that the balance shifts most abruptly from one side to the other. Not to avail oneself of this is the greatest of mistakes.
Many men, it would seem, are desirous of doing what is good, but few have the courage to attempt it, and very few indeed of these who do attempt it fully accomplish their duty in every respect.
Walbank Commentary