You have to be defending, yes.
Hi Sam - but do you have to have "Chosen" to Defend in the first place? I read it like Alan that you do:
...an army that gets the HFA rule has to choose to defend and win the die roll (of course no die roll would be necessary if the opponent chose to attack). So a player that chose to attack and lost the die roll (so ends up as defender) would have forfeited the opportunity to use HFA.
Or are you saying it doesn't matter how you end up as the defender - as long as you are defending you can use HFA if its available?
.
Sorry - don't mean to be pedantic but there is a nice little bit of (potential) subtlety in there if you meant the former (i.e. an army eligible for HFA won't _always_ be guaranteed to have it when defending) - so confirming if there is or isn't that qualification would be appreciated?
:-)