Stubby A True Story of Friendship by Michael Foreman

A dog joins an American group of soldiers while they are training.  He especially likes Corporal Robert Conroy, who adopts him for life.
Stubby performs many heroic deeds and almost dies.   Readers will fall in love with the adorable dog!
Warning: The author describes in detail  how Stubby is blasted through the air from a bomb and how he is covered in mud and blood.  Sensitive readers may be disturbed by this event and the details.   Book sellers have it labeled for preschool-third grade, but with the description of Stubby becoming hurt and the topic of war, I would recommend it for third through sixth grade. 
Pair with Sergeant Billy by Mireille Messier (compare/contrast).
-Borrowed from the library.