Earlier quoted context omitted.
As a person whose first language is not English, I find phrasal verbs one of the most challenging parts of the language. In fact I just searched set upon and was greatly surprised that it means attacking violently! I would have never guessed that from the words alone.
In this case the phrase is a more artistic way of describing the beginning of a fight. Think of "John set upon Mike angrily" as John set, or selected, Mike as his target. It's also a great example of the topic at hand because the same phrase could be used like "The book was set upon the table." Describing a book that was placed on a table. Each version uses the same common vocabulary, to describe wildly different thi…
"John was set up on a date" - someone arranged a romantic encounter for John. "John was setup on a date" - on some specific day John was assembled. "John was set upon a date" - John assaulted a piece of fruit.