  Motivated by wave or Dirac equations on noncommutative deformations of
Minkowski space, linear integro-differential equations of the form $(D+\lambda
W)f=0$ are studied, where $D$ is a normal or prenormal hyperbolic differential
operator on ${\mathbb R}^n$, $\lambda\in\mathbb C$ is a coupling constant, and
$W$ is a regular integral operator with compactly supported kernel. In
particular, $W$ can be non-local in time, so that a Hamiltonian formulation is
not possible. It is shown that for sufficiently small $|\lambda|$, the
hyperbolic character of $D$ is essentially preserved. Unique advanced/retarded
fundamental solutions are constructed by means of a convergent expansion in
$\lambda$, and the solution spaces are analyzed. It is shown that the acausal
behavior of the solutions is well-controlled, but the Cauchy problem is
ill-posed in general. Nonetheless, a scattering operator can be calculated
which describes the effect of $W$ on the space of solutions of $D$.
  It is also described how these structures occur in the context of
noncommutative Minkowski space, and how the results obtained here can be used
for the analysis of classical and quantum field theories on such spaces.
