From Conflict of Nations Wiki
- New research becomes available almost every day. Your research tree is specific to your nation's doctrine, and favours different unit types early on.
- Upgrades are hierarchical. You cannot research late-game upgrades until you research the pre-requisites.
- You may cancel ongoing research at any time. If you do so, you may be refunded a portion of resources depending on the percentage that was reached.
If you are researching an upgrade for an existing unit, you can click the 'i' button to see the unit-specific stats, allowing you to take note and compare how other units might fare.
Your nation's doctrine is key to what research you will likely prioritize during the game. The image below gives you a visual guide to the units which are available first for research per type and doctrine.