How do aliens get stronger?

How do aliens get stronger? - Two Alien Inside Car Wallpaper

Over the course of a playthrough, what determines the strength and quantity of the alien units you fase on missions? For example, do the aliens grow stronger:

  • continuously over time?
  • at specific points in time (e.g. end of each month)?
  • after each mission?
  • as XCOM's squad ranks up?
  • as XCOM's tech advances?
  • as more regions are contacted?

A few implications of this are:

  • If I skip a mission, am I letting the aliens grow stronger while I miss out on resources, or do both sides stagnate?
  • Will pushing XCOM's tech forward only cause the aliens to advance as well?
  • If wait to start a mission (e.g. a facility assault), do I risk it getting suddenly harder after a certain event (e.g. the end-of-month status report)?





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How do aliens get stronger? - Woman Buying a Drink





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