forewarn

I wished to forewarn you of the snare, but I could not then give you my reasons.

We forewarn them that we have taken liberties innumerable with the book.

Also I had learned her identity, and it now remained for me to forewarn her of what was intended.

But if some message could be smuggled in to forewarn them of the enterprise,—would that brace 'em to the assault?