What is the main external conflict of this story? "A young farm boy, who dreams of adventure, lives in a galaxy torn by rebellion and war. He is pushed into the conflict after his aunt and uncle are killed by the Empire for the droids he possesses. After joining a smuggler for cheap transportation, the boy and his mentor are captured by the Empire on their way to rescue a princess and, in the ensuing struggle, the mentor sacrifices himself. The boy and the smuggler save the princess and think they have escaped, only to learn the Empire has followed them to the Rebel base, intending to destroy the planet. Aided by his companions and the last lesson of his fallen mentor, the boy must exploit the hidden weakness of the Empire’s destructive weapon to preserve the Rebellion."

Rebels vs. The Empire
Empire's destructive weapon
rescue a princess
the boy and his mentor are captured