A group of letters from Lord Nelson sent during the Napoleonic Wars are expected to make "thousands of pounds" when they go up for auction next month.
One letter discusses the possibility of war against Spain as well as France, and a possible invasion of Britain by Napoleon's forces.
Once part of a private collection, the letters will be auctioned at Hansons in Etwall, Derbyshire, on 30 September.
Last year a letter written by Nelson while on HMS Victory sold for £17,000.
One letter, dating from 1803, written while Nelson was on HMS Victory as it was stationed at his base off La Maddelena archipelago, near Sardinia, was sent to Maj Gen William Villettes, commander in chief of the British Army in the Mediterranean and then based at Malta.
In it, Nelson discusses Napoleon's views towards Spain's involvement in the war, saying British forces "may be forced to go to war with her for her compliance to the French".
He also worried about the impact of rumours of an invasion from the continent, writing: "Until the idea of an invasion is a little blown over, I fear we shall see no recruits."
The letters are expected to fetch between £3,000 to £12,000 each.
Jim Spencer, head of books and manuscripts at Hansons, said seeing a letter written aboard HMS Victory was "like holding a boarding pass for a time machine".
"Nelson is thinking of the nation's fear of an invasion back home, and he's planning and preparing for anything," he said.
"All of the urgency and wisdom is evident in Nelson's characteristic left-hand."
Vice Admiral Horatio Nelson was born in Norfolk in in 1758, and played a key role in naval victories at the battles of the Nile in 1798 and Copenhagen three years later.
He died at the Battle of Trafalgar, one of Britain's most famous naval successes, in 1805.