That is an oversimplification regarding the French medical instruction.

Medical schools and societies were abolished in 1792 by the Revolution. Two years later the Convention 'hastily set up' military medical schools. The Service de Sante was organized as an autonomous service directed by a central council of medical officers. Later, the Directory abolished that sensible organization and separated the medical service from the medical administration.

Napoleon reorganized that mess from 1800-1804. He did close the army's medical schools after the Peace of Amiens and discharged a number of medical officers. What he did was reestablish the civilian medical schools and 'restored a degree of order and honesty.'

Comparing the war in Spain and Portugal which lasted from 1807-1814 with the invasion of Spain by the French in 1823 is not a logical comparison, based on the length of both events and the resistance of the Spanish in both instances. In 1823 it was negligible.