1) This depends upon who you are playing with - typically you would not have to announce a goblin charge, as it will be very obvious when it is being done for red units, and for blue units, while not as obvious, whether one wants to attack or not with them is the controlling player's decision. If you are playing someone who has a passion for rules , then perhaps announcing would be necessary.
2) In order to use goblin rush, that unit moves two hexes and must end up adjacent to at least one enemy unit. When the controlling player chooses to battle with the "goblin rushed" unit, it must attack if an enemy is adjacent at that time. If no enemy is adjacent at that time then obviously no attack can be made, but the two hex movement is still allowed - one does not have to move it back one hex or anything like that.
3) The decision to use goblin rush is made during the movement phase. Now it gets a little fuzzy, perhaps. The black and white part (as I see it, anyway ): If the goblin unit did not end up adjacent to another enemy during the movement phase and ended up in a similar situation it would not be able to battle, as it would not have done a "goblin rush" action in the movement phase. Now the not so clear part: If the goblin rushing unit moved adjacent to another enemy unit, then later in the battle phase another enemy unit retreats adjacent to it, perhaps it could battle against that retreated unit. Good question for an official answer. I believe the answer would be that in the first instance (did not move adjacent to an enemy during the movement phase) no attack is possible, and in the second (did move adjacent to an enemy unit during the movement phase, then later in the battle phase another enemy unit retreated adjacent to the goblin unit) an attack would be possible
And for the question in your follow-up post: red dwarf foot units have short swords, regardless of their appearance
Another questions about the goblin charge:
1)It is necessary to fix and tell to the opponent player the enemy to be charged at the time of the movements phase, or it is possible to choose it during the attack phase?
2)the globlins are forced to attack in melee the charged enemy but in case of deadh and/or movement (retreat) of the charged enemy, right?
3)It is necessary to decide if goblins charge or normally move during the movments phase, or during the attack phase (for example blue goblins move 2 hex without madea charge, then an enemy troop became close to they, it is possible to declare a charge during the attack phase and attack or not?)?
thankyou very much!!!