This battle was over before it began. The Rebel ground troops were only engaging in a delaying tactic to help with the evacuation. The only reason they had any time to work with was Ozzel's clumsiness. The only real damage done to the Imperials was inflicted by Vader's kidnapped and brainwashed son.
The Rebels are essentially beaten and on the run, Vader isn't really worried about them. His main objective here is to find his son. We find out at the end of the movie from Vader that Luke is his son. Vader didn't find this out at the end of the movie, he's spent this entire movie looking for Luke specifically. Vader knows Luke is his son from before this movie began. If the Rebels were hiding Luke from Vader, how did he find this out? Did the Rebels tell him? No. Vader never says 'I didn't even know I had a son until...'
Vader began searching for Luke no doubt shortly after the first movie, when he realized Luke was missing from Tatooine. This is because it was Vader who was keeping Luke there, not the Rebels. He may not have been 'hiding' Luke (as Luke lives under Vader's surname) so much as he was simply trying to keep him out of this mess of galactic intrique. A big question for the Paradigm is wether Kenobi was the only Rebel who knew Luke was Vader's kid. As discussed earlier, Leia - the leader of the Rebels - surely knew what Kenobi was doing watching Tatooine for nearly two decades. This is why she keeps Luke close at hand. Leia is good at hiding this little tidbit, but gives herself away on Bespin.
When the Imperial troops break into the ice compound, Vader is the THIRD one through the door! Can you imagine Janet Reno being the third one into the Waco compound? Or general Westmoreland being the third one into a Viet Cong command center? This matter of stealing his son is obviously a very personal one to Anakin. And he is pissed! Pity the poor fool Rebel who doesn't get out in time.
The princess slips through Vader's fingers with the aid of Solo. Again. Han takes a moment to kill at least a few stormtroopers before leaving. Just wouldn't be the same without a little murder, would it Captain Solo? Vader is just in time to see the Falcon escape. Easy to imagine he'd be frustrated with the ever-present and unmistakeable Millenium Falcon.
Solo's usual flair for narrow escapes eventually proves useless against Vader's machinations in this movie. Han Solo's major talent in life is being able to get out of tight scrapes. This 'life on the run' doesn't catch up with him so much as Vader catches up with him. Han is transporting the princess, who in turn is hiding Vader's son. Against Vader's personal ire there is no escape.
When Vader finally catches him, Han ends up tortured, frozen, and given to Jabba the Hut as a decoration. The only one who could get him out of that mess is Vader's OWN SON. Really, Han, find new friends.
PREVIOUS--CONTENTS--NEXT
Star Wars---Empire Strikes Back---Return of the Jedi
Phantom Menace---Attack of the Clones---Revenge of the Sith