Because of Queen Apailana's polite and subtle refusal to accept the New Order, the Empire harbored suspicions about her true allegiance. This state of unease kept up for one year, until Darth Vader found out that the Naboo were hiding Jedi refugees trying to escape the Great Jedi Purge. Vader ordered Apailana's execution on the charges of treason, but knowing her guards would expect the assassination attempt on her, he sent Darth Xed to lead the 501st Legion, an elite group of clone stormtroopers, to deal with the Royal Naboo Security Forces.
Naboo's capital of Theed was immediately placed under siege by the 501st when the city would not surrender its queen, however, bold Naboo security guards defended their home with loyal soldiers and AAC-1 speeder tanks. The 501st Legion landed in the royal plazas and engaged the nearby Naboo soldiers, quickly securing their landing area.