Why Did Detering Desert?

Detering sees a cherry tree blossoming in a garden and its reminder of wife and home cause him to desert. He is later caught and court-martialed.

What happens to Detering in all quiet?

The trenches of World War I were truly abysmal, terrifying places, and soldiers witnessed atrocities every day. ... He steals away in the dead of night, escaping the trenches and the front. Ultimately, Detering fails in his escape and is caught and court-martialed. Nobody hears from him again.

Why did Detering want the horses shot?

He becomes injured when a coffin lands on top of him after it is blown up by the shelling. To put him out of his misery - he shoots him, just as Detering wanted to do to the horses (again emphasizes the loss of their humanity and animal instincts).