When does a new buff or a new malus apply if there is a battle underway?

When does a new buff or a new malus apply if there is a battle underway? - Faceless women applying multicolored eyeshadows on wrist for testing

Let say one of these things happens while I paused the game and a fight has been started :

I upgrade my troops for better units
I get a new military technology / idea that modify my army

Will the new buff or malus will apply on my troops during their fight or after it ?

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