18 BBY/2IY: Supreme commander of the Imperial Fleet, Lord Vader ordered the execution of Queen Apailana of Naboo on the charges of committing treason against the empire by harboring fugitive . The 501st was sent to eliminate her but the battle became a disaster the empire for a number of unexpected setbacks: On the land the 501st was shocked to see that the defenders of Naboo was leaded by their former brethren's from the from the famed Torrent company, the most veteran company of the 501st under the command of the traitors captain CT-7567 "Rex", the former second-in-command under Lord Vader. Under his command the Naboo defenders put up a deadly resistance and then lunched an even more deadly counterattack that drove them from the planet. In the bloody engagement, the 501st lost an entire battalion, entirely composed of veteran troops from the clone wars and Operation: Knightfall.
Size comparison between the Archer-Class (Siege ship) and the Jedi Redempthon-class Star Destroyer. (I am trying to stay close to the original lore as much as possible)