Steam, etc...

[Vespers War]

Originally Posted by Mahatatain

I believe that coal mining in Poland is particularly concentrated in Silesia (https://en.wikipedia.org/wiki/Coal_in_Poland) so a particular Margrave might well have control of some resources that Krakow needs, prompting either trade or war, depending on the direction you want your campaign to go in.

There are also hard coal mines in Lower Silesia and Lublin, but the former closed in 2000 and the only one in the latter is Bogdanka. Bogdanka produces about 10-15% of Poland's hard coal.

The largest lignite mine is Belchatow in Lodz; in 2015 it produced 2/3 of all of Poland's lignite, and lignite extraction was almost equal to hard coal extraction (63.1 million tonnes versus 66 million tonnes).

It may also be worth noting that Poland's coal in general is low quality, and they currently import coal for uses that call for higher-quality coal (generally industrial processes).