What is the Moral/Theme of the Trojan Horse Legend?

Don't trust your enemies.

Origin - An allusion to the story of the wooden horse of Troy, used by the Greeks to trick their way into the city. It is recorded in Virgil's Aeneid, Book 2, 19 BC:

"Do not trust the horse, Trojans. Whatever it is, I fear the Greeks even when they bear gifts."

Legend Of The Trojan Horse

The Trojan Horse strategy succeeds brilliantly. Bankers capture control of money supply in America in 1913, by creating the Federal Reserve. Its private, not federal, so, this is an example of hiding something in plain sight.

"Give me control of a nation's money and I care not who makes it's laws" — Mayer Amschel Bauer Rothschild, German banker and the founder of the Rothschild banking dynasty.

Never look a gift horse in the mouth.:P

Beware of Greeks bearing gifts.

Don't take things at face value, especially when dealing with the enemy.

Looks can be deceiving.