After abandoning their headquarters at the Massassi outpost on Yavin 4, the core group of the Rebel Alliance established Echo Base on the Hoth. Alliance engineers worked non-stop to adapt their technology to withstand the subzero temperature extremes of the frigid ice planet. When the technicians were unable to get the T-47s functioning in time, the Rebels domesticated the indigenous tauntaun for use as a patrol mount.
The nerve center of Echo Base was its darkened command center, where General Rieekan issued orders to the rest of his troops. Here, Alliance scanner operators carefully monitored incoming data from the scattered sensors placed by Rebel scouts in the Hoth wilderness.
Protecting Echo Base was a powerful energy shield strong enough to deflect Imperial bombardment. When the Empire arrived in the Hoth system, the Rebels erected the shield, forcing the Imperials to engage in a ground battle. The Rebels speedily evacuated the personnel and equipment they could aboard Rebel transports with starfighter escorts, offering covering fire for the fleeing ships from a massive ground-based ion cannon.
As the transports retreated, the Rebel ground forces and snowspeeder squadrons covered their escape by delaying the Imperials for as long as they could. Rebel troopers dug into snowy trenches, blasting at the incoming Imperials with turret-mounted laser cannons and blaster rifles. The Imperial walkers were unstoppable. The Rebels were routed and Echo Base was overrun.