Atm., we'll have 3 events that steer the availability of gun units (hand gunners, arqubus and musket ... the ladder will be new in the next release).

Canon buildings and its several canons are linked to only one event.

The researchment-question for help:

Who has reliable sources of all available canon units in the game and their appearence on the battlefields?

It would be great to see as result a list of the several types of canons and the dates (not the invention dates, the actual appearence on battlefields).