Your ordered reserve artillery, this turn, will ignore all terrain battle die reduction. In addition, all deadly die side rolled in combat will also score hits and flags may not be ignored for any reason.
If Box Barrage is played and a tank is hit with a flag result, does the tank take a hit?
On one hand a tank will always ignore the first flag rolled against it. On the other, flags cannot be ignored for any reason.
Ultimately, the Combat Card trumps the rules I think?