How we cite our quotes:
I knew that once I left [Topthorn] I would be alone in the world again, that I would no longer have his strength and support beside me. So I stayed with him and waited. (15.1)
When Topthorn dies, Joey experiences the same intense grief that a human might feel over the death of their own best friend on the battlefield. The bonds of friendship make the horses easy to empathize with, don't you think?