He wanted to pretend.

It was his birthright to pretend, in a large active way, and he couldn't carry it out.

The other boys didn't care about making believe soldiers, and running and hiding and shouting and beating Sonny Sahib's tom-tom, which made a splendid drum.

They liked beating the tom-tom, but they always wanted to sit round in a ring and listen to it, which Sonny Sahib thought very poor kind of fun indeed.

They wouldn't even pretend to be elephants, or horses, or buffaloes.
Sonny Sahib had to represent them all himself; and it is no wonder that with a whole menagerie, as it were, upon his shoulders, he grew a little tired sometimes.