  We give a concise axiomatic introduction into the fundamental structure of
classical electrodynamics: It is based on electric charge conservation, the
Lorentz force, magnetic flux conservation, and the existence of local and
linear constitutive relations. The {\it inhomogeneous} Maxwell equations,
expressed in terms of $D^i$ and $H_i$, turn out to be a consequence of electric
charge conservation, whereas the {\it homogeneous} Maxwell equations, expressed
in terms of $E_i$ and $B^i$, are derived from magnetic flux conservation and
special relativity theory. The excitations $D^i$ and $H_i$, by means of
constitutive relations, are linked to the field strengths $E_i$ and $B^i$.
Eventually, we point out how this axiomatic approach is related to the
framework of gauge field theory.
