Not enough time for them to react to your order, and you ignore your warning.
The starship fires a pair of torpedoes directly for you... but they explode early and a flurry of smaller torpedoes break off! Cluster missiles!
The rockets roar down upon you and ravage the street, cutting you off from the raiders and their speeders as you are thrown into the air.
You sensed danger and didn't react.
The explosion has rendered you incapable of action for a moment, as everything becomes smoke and fire and dust. You were deafened by the torrent of blasts and dizzied by the concussive impact. You climb to your feet very slowly, and the ship is already gone by then.
The raiders have taken the opportunity to flee in their speeders!
Some of the militiamen have been killed, vaporized in the explosions. Buildings on either side of the street have been obliterated.
One man emerges from the smoke still standing, however. Sniper rifle in hand, Sherman snaps up the weapon and puts a barrage of shots toward one of the escaping speeders. His aim is true; he catches an engine and it bursts after a solid hit.
He tries for the other, but it has gone out of range.
"Go after them," Sherman says. "We don't have fighters to chase that ship, but at least you can nab these raiders."
Using Dash would be wasteful- it is intended for short distances only, and you would have to make Agility rolls all the while. You run as fast as humanly possible.
By the time you reach the speeder, the raiders have already bailed and are running out ahead of you. With Sherman having blown out one of its thrusters, it can only turn left. You will have to keep running after them.