Colossus by Alexander Cole
Alexander the Great rests in Babylon as he decides which should be his next world to conquer. A war elephant, Colossus, disturbs the peace of the camp when he is provoked to a killing rampage. Only one young mahout has the courage to stop Colossus. And when Alexander notices his bravery, Gajendra begins a meteoric climb through the ranks of the Macedonian army.
Gajendra is fiercely loyal to Alexander, the great General who plucked him from obscurity. But as he rises to become Captain of the Elephants, Gajendra sees how Alexander is being corrupted by luxury and power. Forced to choose between keeping faith with Alexander or with his comrades, and Colossus, his great war elephant, Gajendra must find the strength to make the right decision as Alexander's army approaches the gates of Rome.