Contrary to people's expectation of the Middle Ages, the Middle Ages were one of the most politically and intellectually active periods of history in the Old World. China was undergoing a flowering of culture under the Tang and Song dynasties, while in Europe, the old culture and ethos of the defunct Roman empire was slowly being exported to lands which the Romans themselves never had a chance to dominate, such as northern Germany and Scandinavia. The Dark Ages of Europe cannot be merely seen as a period of lawlessness and ignorance, but one where civilisation slowly seeped northwards and northwards from its traditional bases in the Mediterranean.
All factions have a need for research and technology. With research, you will be able to field better units, as well as afford more of them in order to achieve final victory for your faction.
Research and technologies can be divided into the following:
Upgrades at the library can be considered "game-changing" upgrades that exponentially increase the power of your faction's civilisation on the field. These grant the right to access more powerful upgrades and units, or increase the amount of units you can field or the amount of resources you can receive.
A variety of upgrades are available for units and some buildings. These will either convert units and structures into a more sophisticated form possibly with new or augmented capabilities, or boost what is readily available.
Additionally, administrative reforms can be researched at your Senate to pick a government that favours a more efficient army over a stronger economy.
Strategy upgrades are researched at your Fort, Castle or Stronghold
Fortification upgrades are researched at your Fort, Castle or Stronghold.
Attrition upgrades are researched at your Towers, Keeps and Bastions.
Administrative upgrades are researched at your Nobles' Court and Senate. Some are available only to Christian and Asian factions.
Totalitarian reforms at your Senate are available to all, and grant access to military production bonuses as well as patriot units which boost offensive power of units within their radius of command.
Centralisation and Divine Mandate are researched at your Nobles' Court, but are restricted only to Christian and Asian factions. Centralisation grants the ability to unlock new non-unique barracks and stable units, while Imperial Mandate grants the ability to unlock some new buildings for Orthodox and Asian factions.
Sharia’ upgrades are special technologies which are available only to Muslim factions, and most Muslims have a choice of researching a possible seven out of eight available technologies. Three of these eight are researchable from your Nobles' Court; the rest being available only from your House of Worship.
Buildings associated with economics have a variety of technological upgrades that can be researched in order to improve productivity further. These are normally associated with the creation of buildings, new units and speeding up the gather rates of citizens working at mines and the like.
Administrative upgrades are researched at your Nobles' Court and Senate.
Libertarian reforms are available at the Senate and will improve your economy by lowering upgrade costs or increasing your caravan limit. However, it must be borne in mind that government technologies are mutually exclusive: if you pick a libertarian tech, you will be unable to pick its corresponding totalitarian upgrade.
Sharia’ technologies can be unlocked by Muslims at their Nobles' Court. There are three in total; two of which may be chosen to improve production and research.