Summary: Armies of hundreds (or in the case of goblins, even thousands) roam the map and attack sites, but give up after a single casualty. What gives?
The context for these observations is a normal region, generated with the settings that come as a default when you pick advanced world generation. History length was about 140 years, and there have been 20 years of play as fortresses and adventurers, so it's the year 162 when these legends screenshots were taken.
To get a good sample, I instigated multiple wars between combatant civilizations. This is easy to do: just park a fortress in a provocative location and your parent civ and your neighbors will be at war as soon as you somehow warrant and ambush or a siege. Other battles are from wars the AI just started on its own. Let's a go!
Case in point, the "War of Striking", a still ongoing conflict between elves and goblins that began 11 years ago in 151 when the elves attacked. This is the first battle of that war:
Nothing unusual here (except for suffering 3 casualties out of 2 elves). The defenders won fair and square and it looks like about what you'd expect. What followed was a year of small-scale attacks on this goblin site that often succeeded, but the elves never moved in or destroyed it after winning, so the site simply repopulated. Then suddenly this:
They counterattack by coming down hard on an elven settlement, numbering over 1,500 units. But then they give up after about 60 casualties... okay, that's fair. They might do that in fortress mode as well. But like all the wars I observed, the conflict soon degenerated into this:
This is just a small sample, the war is producing many of these battles per year that end as soon as the attacker takes a single casualty:
Why do they quit so soon? Is this a sieging bug or intended behavior somehow. This happens across all wars with every race, it's just the most hilariously noticeable with the goblins because they field such enormous armies. Also, these giga-armies don't seem to properly materialize for you to challenge with your adventurer (yeah, you can kill a bunch when they're camped around), so are they maybe not even showing up for the simulated battle with the settlement?
I'm curious to hear everyone else's take on this.