Grant the thesis of Enders' Game; that one could find and specially train children to become superlative strategists and tacticians and military leaders. It does not follow that they have the skills required to assemble an army or lead a country--things that require some adult wisdom or street smarts. In these two sequels (I haven't read Shadow of the Giant), Card explores what happens when his superintelligent children and adolescents wind up immersed in adult national power struggles, and not necessarily having a good feel for all the nuances of leadership and control.
The central character is the doomed Bean, and Achilles is his nemesis. Power struggles and eventually wars between countries make the children great prizes.
They make for good reads. The character of Peter is unexpectedly benign, compared to Enders Game. Card and Niven both like writing about superintelligent creatures, and both have the same trouble describing characters more intelligent than they are--it works for a while, and then the reader starts to feel like he's being set up. I'll probably get around to Giant after a while.