I don't know if it's a bug (found in the game or the mod I'm using - "True Endless Speed") but I've ran into a (almost) never ending cycle of battles. There was a tiny set of isles next to my continent. I left it alone, but in the medieval era I noticed aggressive independent peoples coming from it to raid my continent. So I decided to get rid of them. I sent a fleet to wipe out their boats and an army to wipe the IP outpost. BUT my army ended the turn one tile apart from the island with the outpost. In the beginning of each turn IP were embarking on the ships and attacking my army. Fortunately my fleet was nearby so I was winning every battle, but after the battle my both fleets were left with no movement points. And immediately at the beginning of the next turn IP were spawning new full stack and doing the same they did a turn before. The problem is that IP were spawning every turn. I could wipe them out only to see another army appear out of nowhere next turn. I cound't move my fleets away to prevent the battle because they had no movement points left after the previous battle. I couldn't retreat, because one of the units in the attacked fleet had trait which did not allow me to do that. That cycle ended itself when IP outpost disappeared on its own.

I don't know what was the cause of that aggressive spawn rate (new army each turn), but if that's caused by the latest patch and not the mod I'm using then I'm not sure it's as it should be.

I checked with the designers, and they've told me that in an unmodded game, the fastest spawns should be 5 turns for Peaceful IPs and 8 for Aggressive IPs on Blitz speed, while the lowest speed will be about four times as long.

This could be a bug, but it is quite likely that mods affecting game speed may have unexpected effects on the spawn rate. So please let us know if you run into this again, especially in an unmodded game.