Something I observed while browsing Memory Alpha.
The Federation and the Klingon Empire run parallel to each other in terms of conflicts they’ve had. They share several conflicts (Federation-Klingon Wars, Cardassian Wars, Dominion cold war, Dominion War, Temporal Cold War). They’ve even had their own invaders. The Hur’q that plundered Qonos, and the Romulans that attacked Earth during the Earth-Romulan War. I know of no Qonos-Romulan War occurring between the 9th and the 22nd century, but with Klingons being warp capable at early as the late 1940s, anything possible.
But, there are a couple of conflicts that remain distinct to them each. The Federation have the Galen border conflict with the Talarians & the Tzenkethi Wars durng the Lost Era. While the Klingons had a civil war during TNG, which was influence by Sela and the Romulan Empire.
I'm wondering, with there being a few gaps largely unexplored and unfilled in Trek history (ENT and The Cage, The Lost Era, PIC and DIS S3) if the inverse happened to both powers. In that the Federation has its own civil war (logic extremists don’t count), and if the Klingons had their own Galen border conflict with Talarians and their own Tzenkethi Wars to further highlight how they run parallel to each other.