Vaughn Heppner, the author of Alien Shores discusses correlation between intergalactic invasions and the Age of Sail.
I think the best model to understanding future faster-than-light space invasions is the Age of Sail.
In those days, the Spanish, Portuguese, Dutch, French and English built worldwide empires. The heart to each of their territories was the cannon-armed sailing ship, the caravel, carrack and galleon. In relation to the time and space of their milieu, my argument is that sailing ships are remarkably similar to what most novelists imagine future starships would be like.
Voyages took weeks, sometimes months. In an intergalactic empire, trips from one star system to another would likely take just as long. Even with a warp drive, crossing a vast expanse like the Orion Arm would be a daunting adventure.
In the age of sail, a message traveled as fast as a ship or as fast as a horseman could carry a letter. Unless some magical system is employed, the same would be true in an interstellar empire. As an aside, I wrote about one such magical system in Strotium-90. Telepathic twins on two different worlds became the only instantaneous communication line society possessed between star systems. How fast would thought travel? Faster than anything else was my answer.
In any case, the speed of communication given the long travel times becomes critical. The age of sail provides us with a clue as to how events would unfold in a galactic empire under attack.
In all likelihood, an invading fleet would not have quick communication with its homeworld. Just as an English naval commander off India became a law unto himself, so would a space admiral be. He would have to make drastic, interstellar-shattering decisions without being able to phone home for advice or new instructions. He also wouldn’t have access to quick reinforcements. To win, he has to use what he’s hauled with him these many weeks.
In the same way, the defending viceroy of an intergalactic empire would have tremendous power and authority. It could take weeks, maybe months to send a report to the emperor and receive a reply. Decisions would need to be made immediately.
These days, the idea of being cut off is difficult for us to comprehend in our guts. We’re used to cellphones and instant TV coverage or internet footage. The loneliness of leaving everything behind and entering a star system with who knows what kind of surprises in store could make for a terrifying journey. It might also make invaders cautious until they’ve sent in scouts. Once a catastrophe strikes a starship or a fleet far from home, the situation could become dire indeed.
In my latest novel, Alien Shores, the hero struggles to know what to do once disaster has struck. The aliens in the Fenris System—230 light years from Earth—pose a terrible threat to humanity. If the hero fails to commandeer a Teleship to reach home, there’s no way to warn mankind of the approaching danger. An alien fleet might gather and attack the solar system with as much surprise as Native Americans felt upon seeing Christopher Columbus’ sailing ships off their shores.
On Earth in our day, we’ve radically shrunk travel time and communication lag. Intergalactic empires and their invasion would dramatically expand both, perhaps to an even greater extent than humanity experienced in the age of sail. To understand what the future has in store, a close study of those days might reveal what it would be like with an empire among the stars.