I had to read and reread, not just your question but the letter itself.
I kept reading the bottom of your question instead of the bottom of Gil-Galads letter :
The darkness that is to come is filled with hatred for us, but it hates you no less. The
Great Sea will not be too wide for its wings, if it is suffered to come to full growth.
That if nothing is done, even Númenor is in jeopardy.
Is that, what you were looking for? If not, I don't have a clue....