Admiral Ozzel commanded the Super Star Destroyer Executor, Darth Vader's mighty flagship and the linchpin of the squadron searching the galaxy for the Alliance's secret base. Ozzel led the initial attack on Hoth, but his choice of tactics infuriated Vader, leading to a sudden and permanent demotion.
Used to having his orders obeyed without question, Darth Vader had little patience for Ozzel's thoughts on the hunt for the Rebel base, blaming him for coming out of hyperspace too close to the Hoth system and allowing the Rebels to prepare a defense. Infuriated, he strangled Ozzel with the Force.
The ambitious Captain Piett saw Ozzel's arrogance and habit of talking back to Vader as a danger to the man's continued health -- but an excellent opportunity for Piett to continue his advance through the Imperial ranks.
Nineteen kilometers long and bristling with laser cannons, the Executor was one of the mightiest warships to ever cruise the galaxy's hyperspace routes -- and Ozzel regarded himself as the natural choice to command her.