I know some gentlemen that allways insisted on a difference between the two, however I will except your view, as would most people.<quoted text>
I would say that the meanings of 'alert' and 'vigilant' are interchangeable.
I would add that situational usage would make 'alert' the word more likely to be hollered by officers in the noise of battle because its very sound is more forceful, it has fewer syllables and is more amenable loud and carrying utterance.
But that is peripheral.
In all other respects I would equate the conceptual thrust 'alert' and 'vigilant'.
I don't know if we are now moving on, but I may have to go out shortly. In which case I would have to reply to part B at a later time.
By the way, of the few hours you sleep, what percentage would you call quality time ?