How do you think ended is being trained to save the world?

Ender is being treated as a means to an end. He is being manipulated and moulded into exactly what the military needs to get their job done. I suppose it is sad that Ender loses his childhood but then Ender or any other child is expendable if the survival of humanity is at stake. The fact that, in the end, humanity was never in any real danger from the Buggers brings a tragic irony to human behaviour that we have seen since man entered history.