technically, that is incorrect. Embassies and consulates, yes. Military bases, no.
EDIT:
http://www.state.gov/documents/organization/86755.pdf
Despite widespread popular belief, U.S. military installations abroad
and U.S. diplomatic or consular facilities abroad are not part of the United
States within the meaning of the 14th Amendment. A child born on the
premises of such a facility is not born in the United States and does not
acquire U.S. citizenship by reason of birth.