Here's how it is...

Earth-that-was got used up.

We moved out -- terraformed and colonized hundreds of new earths; some, rich and flush with the new technologies; some, not so much. The central planets -- them as formed the Alliance -- decided all the planets had to join under their rule.

There was some disagreement on that point.

After the Unification War, many of the Independents who had fought and lost drifted to the edges of civilization, far from Alliance control. Out here, people struggle to get by with the most basic of technologies. A ship will bring you work; a gun will help you keep it.

A captain's goal is simple: find crew, find a job... keep flying.

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The Independent Faction was the name of a group that fought the Alliance during the Unification War. The group was nicknamed 'Browncoats', due to the brown colored trench coats they wore (Alliance troops were nicknamed 'purple bellies' due to the coloring of their own armor).

One of the reasons the faction was formed was to attempt and prevent the alliance from creating a "better" and "more peaceful" people.

The faction was created when the core worlds formed the Alliance and declared war on any planets that resisted efforts to unify the rest of the planets under Alliance control (thus the name Unification War). After the war ended, surviving faction members migrated towards the outer planets, where Alliance control is more tenuous.

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In the Firefly universe, Browncoats were soldiers who fought for the Independents, who lost to the Alliance in the Unification War. They were named after the simple, brown leather trench coats they wore as uniforms. They also wore red scarves around their necks. The simplicity of their gear was greatly due to the fact that technology and resources were scarce on the Outer Planets. Conversely, the Alliance's soldiers were called "Purple Bellies", because of the purple tinted body armor they wore on their chests.

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Firefly / Serenity's creator Joss Whedon says about Browncoats:

"Firefly went on the air a few years ago and was instantly hailed by critics as one of the most canceled shows of the year. It was ignored and abandoned and the story should end there, but it doesn't, because the people who made the show and the people who saw the show (which is...roughly...the same number of people) fell in love with it a little bit...too much to let it go, too much to lay down arms when the battle looked pretty much lost. In Hollywood, people like that are called 'unrealistic'... 'quixotic'... 'obsessive'.

In my world, the're called 'Browncoats'."

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Take my love, take my land,
Take me where I cannot stand...
I don't care, I'm still free!
You can't take the sky from me.

Take me out, to the black,
Tell 'em I ain't comin' back...
Burn the land and boil the sea!
You can't take the sky from me.

Have no place I can be,
Since I found Serenity;
But you can't take the sky from me.

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