Slitherine

I'm currently playing the Kiev scenario in the 41 campaign, level field marshall.

I have noticed that soviets new units (usually, 15 strength militia) seems to be created from time to time during the course of the scenario.
It happens in other scenario too, how does this units creation is trigerred? Is it related to captured city left empty? Is there a way to prevent it?

Thanks

Welcome to the forum, Delta66.

The city flags can be used to produce units by the owning player (or the AI) after a delay of 2 turns from the turn of its capture. This can be prevented by either capturing the flag yourself, of course, or putting a unit adjacent to the flag. Strategic bombers can be used to neutralise the flag, too, which has a similar effect but that seems to be a random occurrence.

Thank you very much. I thought it wasn't at random, but I had no idea of the specific rules.