It is possible those new ships are called Mark One StarHawk New Republic class BATTLESHIPS, first introduced in the novel “Aftermath” The novel described the StarHawks as being shaped like Hatchets at the front, medium-sized, sporting laser cannons and missile pods, and a special tractor beam weapon capable of moving…

In ESB, the Rebels probably didn’t have the equipment. That or all their fighters were dedicated escorts and all they had were slower underpowered speeders. And keep in mind the range they were fighting on Hoth. Also, Pablo Hidalgo on Rebels Recon said that the AT-ATs on Hoth were a different and more heavily armored…