Conversation so far:
Does Voldemort appear in Harry Potter and the Half-Blood Prince?
Voldemort does not appear in Harry Potter and the Half-Blood Prince.
Was there any flashbacks?
In a series of flashbacks, using the pensieve as a plot device.
Who was the author of Harry Potter and the Half-Blood Prince?
Rowling.

Question: Did Voldemort have to assault anyone?
Self-contained rewrite: Did Lord Voldemort have to assault anyone in Harry Potter and the Half-Blood Prince?