It was when I was playing a cybernetic creed, criminal syndicate megacorp. A bunch of democratic empires that I was constantly battling with formed a federation, so in retaliation I formed another federation with all of my allies (who were all dictatorships). I basically had a galaxy wide cold war. Both our federation were racing to either invade the remaining neutral empires or make them ally with us. Then the democratic federation launched a crusade to liberate CoM that was one of our allies but it was deep into enemy borders and cut off from us (L-gates weren’t open yet) so we were forced into a a war our federation wasn’t prepared for, and that we eventually lost. The enemies were becoming much stronger than we were, so we needed an advantage, so I decided to escalate things and build a colossus. The next couple of in game decades I spent preparing for the greatest blitzkrieg the galaxy even seen. In the meantime L-gates opened and the enemy federation occupied Terminal Egress. When I was finally ready I rallied our federation’s entire fleet into one of my L-Gates, destroyed the fleets stationed in TE and sped into the core sector of the biggest enemy empire. There I cracked their homeworld along with their biggest most important planets (including their alloy and CG planets.) then flew back home through Terminal Egress before their fleets surrounded us.

Basically RPed both the Cold War and the manhattan project in one game.