This cannon was a heavy turbolaser located near the thermal exhaust port on the first Death Star.
During the Battle of Yavin, the Rebel battle plan required pilots to navigate a trench along the surface in order to reach the thermal exhaust port—a direct hit from a proton torpedo would trigger a chain reaction to destroy the station. However, before the assault on the trench could begin, the Rebels needed to eliminate the cannon on the surface. Since the cannon was too heavily armored to attack directly, Rookie One and Ru Murleen of Blue Squadron opened a gap in its shielding and flew into the superstructure. There they destroyed several power relays, disabling the weapon and clearing the way for the Alliance forces to begin their trench runs.
During the Battle of Yavin, the Rebel battle plan required pilots to navigate a trench along the surface in order to reach the thermal exhaust port—a direct hit from a proton torpedo would trigger a chain reaction to destroy the station. However, before the assault on the trench could begin, the Rebels needed to eliminate the cannon on the surface. Since the cannon was too heavily armored to attack directly, Rookie One and Ru Murleen of Blue Squadron opened a gap in its shielding and flew into the superstructure. There they destroyed several power relays, disabling the weapon and clearing the way for the Alliance forces to begin their trench runs.