  The growth of the most massive black holes in the early universe, consistent
with the detection of highly luminous quasars at $z> 6$ implies sustained,
critical accretion of material to grow and power them. Given a black hole seed
scenario, it is still uncertain which conditions in the early Universe allow
the fastest black hole growth. Large scale hydrodynamical cosmological
simulations of structure formation allow us to explore the conditions conducive
to the growth of the earliest supermassive black holes. We use the cosmological
hydrodynamic simulation BlueTides, which incorporates a variety of baryon
physics in a (400 Mpc/h)^3 volume with 0.7 trillion particles to follow the
earliest phases of black hole critical growth. At z=8 the most massive black
holes (a handful) approach masses of 10^8 Msun with the most massive (with M_BH
= 4 x 10^8 Msun ) being found in an extremely compact spheroid-dominated host
galaxy. Examining the large-scale environment of hosts, we find that the
initial tidal field is more important than overdensity in setting the
conditions for early BH growth. In regions of low tidal fields gas accretes
'cold' onto the black hole and falls along thin, radial filaments straight into
the center forming the most compact galaxies and most massive black holes at
earliest times. Regions of high tidal fields instead induce larger coherent
angular momenta and influence the formation of the first population of massive
compact disks. The extreme early growth depends on the early interplay of high
gas densities and the tidal field that shapes the mode of accretion. Mergers
play a minor role in the formation of the first generation, rare massive BHs.
