Isso é " Armadilha de Entidade " de Fredric Brown.
Conforme descrito por outro pesquisador
An energy creature becomes trapped in the head of a soldier as he dies (the only remaining part of the soldier is his head after an explosion and the energy creature is "sucked in" and trapped by the matter when the soldier dies.) it is controlled by the memories of the dead soldier. Through the powers of the energy creature, it rebuilds the body and eventually becomes president of the united states but has a ultra nationalistic view of the world because of the memories within the head. Two other energy creatures eventually find the trapped energy creature and help free it. The only thing left of the man when the energy creature is freed is his head which falls on a table.
I have a feeling the Soldiers name was John Dix or similar. I read it in a book of short science fiction stories.