  Nuclei colliding at very high energy create a strong, quasi-classical gluon
field during the initial phase of their interaction. We present an analytic
calculation of the initial space-time evolution of this field in the limit of
very high energies using a formal recursive solution of the Yang-Mills
equations. We provide analytic expressions for the initial chromo-electric and
chromo-magnetic fields and for their energy-momentum tensor. In particular, we
discuss event-averaged results for energy density and energy flow as well as
for longitudinal and transverse pressure of this system. Our results are
generally applicable if $\tau < 1/Q_s$. The transverse energy flow of the gluon
field exhibits hydrodynamic-like contributions that follow transverse gradients
of the energy density. In addition, a rapidity-odd energy flow also emerges
from the non-abelian analog of Gauss' Law and generates non-vanishing angular
momentum of the field. We will discuss the space-time picture that emerges from
our analysis and its implications for observables in heavy ion collisions.
