The Battle of Blood Ridge was a major event in Rick's life and one of the few emotionally important moment's in his history. It's significant because during the battle, Rick began developing a connection to Birdperson and asked if they could truly be 'best friends' (there were homosexual connotations, but this remained unclear). Birdperson declined his offer but said that Rick could use the 'beacon' anytime to contact him. This rejection deeply impacted Rick, and he still refers to the "Battle of Blood Ridge" as his "Vietnam'', presenting itself as a form of PTSD within Rick.
The battle itself was fought against the Galactic Federation by Birdman's people and many others, including Rick. They won the battle and Birdperson said the fighting was "indeed very bad-ass". A friend named Geardude fought along side them
Rick left Birdperson behind in a huff with his feelings very hurt; but we know they became friends again and stayed friends for decades after.
We get to see the battle in the episode Rickternal Friendshine of the Spotless Mort.
You can watch Birdperson's memory of the battle here https://www.youtube.com/watch?v=CXcA-luO0uM