First strike (This creature deals combat damage before creatures without first strike.)
Whenever Preeminent Captain attacks, you may put a Soldier creature card from your hand onto the battlefield tapped and attacking.
Any abilities of the Soldier creature card that trigger “Whenever [this creature] attacks” won’t trigger because the creature was never declared as an attacking creature.
You choose what the Soldier you put onto the battlefield is attacking. It doesn’t have to attack the same player or planeswalker as Preeminent Captain.