On first inspection by Rebel leaders, the stolen plans of the Imperial Death Star only make the situation look hopeless. The battle station is even larger and more heavily armed than the Rebels expected. However, Jan Dodonna spots a crucial weakness in the Death Star's design, which might allow a one-man fighter to set off a chain reaction in the station's core reactor.
The weak point is a small thermal exhaust port, connected directly to the main reactor. This exhaust port, only two meters wide, is protected in a trench running 50 kilometers across the Death Star's surface, toward the upper pole. Turbolaser turrets protect most of the surface with a deadly hail of fire, but the far end of the trench is thinly defended. A ship maneuvering into the trench at this point might have a chance of surviving the run and bombing the exhaust port.
Dodonna's plan is carried into action, and the bold Rebel pilots in X-wing and Y-wing fighters find themselves racing down the Death Star trench at terrific speeds. While in its northern section the trench does offer shelter from the turbolasers, the Rebels soon face the devastating pursuit of TIE fighters, led by Darth Vader himself, and one by one the freedom fighters are eliminated until hope hangs by a thread.