The Fall of Rome
In The Cloak's world, I'm experimenting with the idea of parallel dimensions. The problem with alien races is not even really the vastness of space, but a matter of timing. It is simply logical that given that there are other planets around other stars, there are planets similar enough to Earth to support life. But, Homo sapiens sapiens, as a species, has been around for fewer than 100,000 years; our history extends back only 5,000 years. What are the chances that on those other Earth-like planets there would be another species capable of radio communications within that 5,000 year window? Not being a doomsayer, let's say our species has another 20,000 years of history left to us. In a planetary lifespan of 4,000,000,000 years, what are the odds that a radio-capable species will emerge within that 25,000 year window? I believe in alien life, and much as I love Star Trek and Star Wars, I just don't think the timing favors contact.

One way around this problem is the remain within the window of human opportunity. Until the communications and transportation revolutions of the 19th and 20th centuries, what did the civilizations in Western Europe and South Asia have in common? What coudl be more alien than 6th century China and North America? So, imagine how alien a culture could be if history had turned out differently? (I know, this contradicts my usual hatred for bullshit alternate histories. What can I say?) The Cloak's Earth is in contact, almost in league, with two alternate Earths: British Earth and Nazi Earth.

On British Earth, the Continentals lost the Revolutionary War. Britain eventually conquered and colonized all of both America and Canada, and with the resources of the combined Dominion of North America, easily defeated the German Empire in the Great War. No Nazi takeover in Germany, no Communist revolution in Russia, no nonviolent rebellion in India. Even in 2004, the sun never sets on the British Empire.

On Nazi Earth, those bastards invaded France, not Poland, in 1939. The RAF was annihilated and Britain subdued by 1941. Fighting a war on only one front, the Soviet Union all the way to the Urals was conquered by New Year's Day 1942. After Pearl Harbor, Germany declined to declare war onthe United States, which went on to defeat Japan, culminating in a bloody invasion of the Home Islands. In 1946, with the gains of 1939-1942 solidified and consolidated, the Nazis launched a sneak nuclear attack on a USA still recovering from the shocking casualties from Japan, destroying all the major cities of the Eastern seaboard. In 2004, the sun never sets on the Third Reich. Fucking Nazis...

Why would The Cloak ally with alternate versions of his history (which is our history)? Because on a third Earth, the Roman Empire never fell. There were no Dark Ages and by 2004 (2757 by their calendar) the Pax Romana extends across the entire globe. But for Rome's ambitions, the world is not enough. The legions of a Rome more technologically advanced than our world have found a way to breach the dimensional divide and are subjugating all the different Earths they encounter. They are known as the Pax and their creed is simple, "Rome is above the nations."

In thinking about how Rome might have persevered, I've been studying up on Roman history. I'm a big fan of Scipio Africanus, but what Rome needed was a Cato (the Censor, not the Younger) to keep her true to the virtues that allowed a tiny Latin settlement to conquer first Italy, then Carthage, and finally the known world. A Cato, and no Hadrians. Hadrian is celebrated, but I cannot fathom why. He voluntarily returned imperium over Mesopotamia to Persia. WHAT?! This is Persia we're talking about, the Parthians! The jerks who killed Crassus and swallowed up entire legions! You cannot just return territory that Trajan wrested from them. In my admitedly sketchy history, the Western Roman Empire was not overwhelmed by barbarian invasion, but managed to integrate the new population into the Empire; in the 5th century Constantine's division of the Empire ws reversed; and in the 6th century the reign of the Caesars was ended by a return to the Republic. We must remind ourselves that most of Rome's conquests came not under the autocratic emperors, but the quasi-democratic consuls. No surrender, no retreat, no Hadrians. Expand or die.

The Cloak's Earth (almost, but not quite our world)
British Earth (the Empire)
Nazi Earth (the Reich)
Roman Earth (Terra Romana)

And of course, Mars....