Attack Pattern Delta was one of three Rogue Doctrine attack formations developed by Commander Luke Skywalker and Alliance to Restore the Republic tactician Beryl Chiffonage, with help from Risiev Credal, for use by the T-47 airspeeders stationed at Echo Base on the planet Hoth. Skywalker and Chiffonage knew they would be facing Imperial walkers in the upcoming battle after the Rebel base had been discovered. However, until the actual thick of combat, the fact that the armor of an AT-AT walker was too strong for the snowspeeders' laser cannons was unknown.