The intended audience is people without previous war game knowledge. They may only have a vague notion of what 'strategy' and 'tactics' are, so don't assume much there. Rather than give specific 'click here, type there' instructions, prefer to move the reader from how the game should be played to describing Wesnoth's world and get them excited enough to want to see for themselves. Try to use simple words for a widely varying range of players, of all ages, many of whom do not use English as a first language.
Definitions, like campaign and unit, should be given early on because it makes the rest easier to write. By immediately giving a mindset and overview, the reader can then use it when discussing details about hit points and Fog of War.
Mentioning unit names is a bad idea, since the reader is likely still trying to get the game running and specific units have no meaning to them. There is no real discussion on strategy. The material needs reorganising. The scenario sections should follow each other. The word unit should be introduced very early, but without detail. A unit section can describe units more fully. The words troops and army aren't really suitable for Wesnoth, unit seems all that's needed. Some material is duplicated and should be cleaned up.
I'm not sure what is the best approach when dealing with villages and recruiting. Villages affect many aspects, but are part of the world. Perhaps it might be better to have a Gold system section instead.
I think the pages MainlineScenarios, UserScenarios, and BeginnerScenarios should be called MainlineCampaigns, UserCampaigns, and BeginnerCampaigns.