In the first battle you did not play a fort and lost the unit because of the sword on Jaime that Lannister played. Second time you did play a one fortification with Dagmer, however Lannister had 3 swords on Gregor so you only negated one of his swords, in which case you would've lost 2 units instead of 3, if you had that many.

I would advise you to read about card effects in the rulebook: https://www.thronemaster.net/files/rules_2nd_edition.pdf (on page 19)

A common misunderstanding. One fortification icon cancels one sword icon, it doesn't protect a unit from getting killed directly.

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