Situation
Empire strikes with one unit.
1-Dwarf: sacrifice slayers of Karak Karak Kadrin (which, as the cost of the action go to the discard pile).
2-Empire responds by playing an iron discipline, with the action of the dwarf player fails if you do not pay 4 resources.
3-Dwarf (which only has one resource) plays "stand your ground"to bring back a game to the slayers.
4-sacrifice Dwarf Slayers to destroy the attacking unit.
The latter action should cost 4 resources or not? I think so, but the rules are not entirely clear to me at this point
Reasoning: The slayers are not in play until it is resolved successfully "stand your ground", so his sacrifice to play for the second time, wait for the outcome of such tactics is the last of the LIFO stack. Once resolved "stand your ground", have a right to return to abort the game at that time? Or has solved the whole LIFO stack before playing new shares? (In which case the iron will is already in play and therefore declared objective of the imperial unit costs 4 resources or the action fails. I believe that as needs resolve "stand your ground", you must "pass" to continue to play and trigger responses LIFO stack, which is played out completely, and then open a new stack of actions with the second sacrifice of the murderers (so that the iron will and is active).
The rules do not specify that happens?, but I think once the battery begins to resolve Lifo whole has to be solved, as it has begun to solve precisely because no player reported any response action ... and therefore can not declare a new action until the end of the chain. If you want to respond to something you have to do before you begin to resolve the string, but missed your opportunity because you can not respond to haver the "past" in your turn to play action.
Sorry for my bad english.