  The orbital decay of a perturber within a larger system plays a key role in
the dynamics of many astrophysical systems -- from nuclear star clusters or
globular clusters in galaxies, to massive black holes in galactic nuclei, to
dwarf galaxy satellites within the dark matter halos of more massive galaxies.
For many decades, there have been various attempts to determine the underlying
physics and time-scales of the drag mechanism, ranging from the local dynamical
friction approach to descriptions based on the back-reaction of global modes
induced in the background system. We present ultra-high-resolution $N$-body
simulations of massive satellites orbiting a Milky Way-like galaxy (with $>
10^8$ particles), that appear to capture both the local "wake" and the global
"mode" induced in the primary halo. We address directly the mechanism of
orbital decay from the combined action of local and global perturbations and
specifically analyze where the bulk of the torque originates.
