@mattblaze @SteveBellovin @karlauerbach Even though the departure could not be secret, there was could be tight security.
Napoleon famously kept the destination of his Mediterranean invasion fleet secret, to inhibit pursuit by the Royal Navy, with its faster warship-only fleet. Nelson sailed back and forth across the Med, catching news of where Bonaparte had been, only catching up with the French fleet after they had already disembarked Napoleon and his army in Alexandria, from where they rapidly conquered Egypt (a complex power play to separate India from Britian, the plunder of India paying for the British forces in the Napoleonic Wars).
Then, being Nelson, he wiped out the warships of the French fleet in the Battle of the Nile despite the French pre-prepared and advantageous position. (The streets of my Port Adelaide -- an Empire maritime town -- are named after this battle, it was widely admired as his technically best victory.)
Anyways, it's clear what a difference even one telegram could have made, and why the British Empire paid such large sums for undersea cables, initially of short life.