Gallop◆◆ The horse Strides twice, with its Speed increased by 10 feet.
Undead Steed Undead and creatures allied with them can Command a skeletal steed without needing to attempt a skill check.
Source: Pathfinder Monster Core
Running this fight? Add the skeletal horse to the initiative tracker: type its name and the AC, hit points and Perception for initiative fill in, and the book button shows this stat block mid-fight.