The ground tactics card Dig In says that you can Discard a tactics card to Block 2 Damage.
I took this to mean that you had to discard a different card and that the Dig In card itself is spent/discarded just by the act of playing it.
My opponent (and son-in-law) took it to mean that you could just discard the Dig In card itself and block 2 damage or discard a different card and keep the Dig In card for future uses.
The only example I found for that was in an example of play article someone discarded a different card but there was no mention of whether the Dig In card was kept afterwards or not.
We house ruled it my way (Spend card and discard another) with a dice roll off but were hoping for an FAQ on this.