  The Lichnerowicz conjecture asserts that all harmonic manifolds are either
flat or locally symmetric spaces of rank~1. This conjecture has been proved by
Z. Szab\'{o} \cite{Sz} for harmonic manifolds with compact universal cover. E.
Damek and F. Ricci \cite{DR} provided examples showing that in the noncompact
case the conjecture is wrong. However, such manifolds do not admit a compact
quotient.
  In this paper we study, using a notion of rank, the asymptotic geometry and
the geodesic flow on simply connected nonflat and noncompact harmonic manifolds
denoted by $X$. In the first part of the paper we show that the following
assertions are equivalent. The volume growth is purely exponential, the rank of
$X$ is one, the geodesic flow is Anosov with respect to the Sasaki metric, $X$
is Gromov hyperbolic. In the second part of the paper we show that the geodesic
flow is Anosov if $X$ is a nonflat harmonic manifold with no focal points. In
the course of the proof we obtain that certain partially hyperbolic flows on
arbitrary Riemannian manifolds without focal points are Anosov, which is of
interest beyond harmonic manifolds. Combining the results of this paper with
the rigidity theorem's of \cite{BCG}, \cite{BFL} and \cite{FL}, we confirm the
Lichnerowicz conjecture for all compact harmonic manifolds without focal points
or with Gromov hyperbolic fundamental groups.
