Welcome back! First of all,
Holy Shit where do I even start...
The Immortal War is (sort of) still going, but is no longer a big thing. Warhead is rarely active anymore due to health problems and a lot of other people from way back then are no longer around.
There was a war called the AN-TA War that was the Third Alliance (a bunch of German factions) vs the Allied Nations (most everybody else). The conflict ended peacefully

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Two of the big players nowadays are the Imperial Magikstrate and what is now known as Unified Republik of Poland. They are played by RedRover and Duerer respectively, both of them also have many other cool factions.
The Space Nazis and Space Commies teamed up to invade Poland recently, but were repulsed.
There is a fairly new faction called M-Throne played by Kaplan that probably has the largest IRL army in Brikwars and is gearing up to possibly invade the Brikverse.
Other factions who have been fairly active recently include Trattoria, played by Colette, and the United Systems Alliance, played by Silent-sigfig (I believe he was active in your day).
Probably 70% of the people active now were not around back in 2011, I was only a lurker back then. Thus, you've missed a ton of new factions and battles and events and I've only just scratched the surface, I'm sure others will help you get caught up though.
Right now we have a build contest called the Blarney Build going on, you can see the deails in the armory forum. I encourage you to enter one (or more) of those awesome ships in, they look badass.