  We present results from a 220-ks observation of the galactic supernova
remnant (SNR) W49B using the Advanced CCD Imaging Spectrometer (ACIS) on board
the Chanrda X-ray Observatory. We exploit these data to perform detailed
spatially-resolved spectroscopic analyses across the SNR with the aim to
investigate the thermodynamic properties and explosive origin of W49B. We find
substantial variation in the electron temperature and absorbing column toward
W49B, and we show that the mean metal abundances are consistent with the
predicted yields in models of bipolar/jet-driven core-collapse SNe.
Furthermore, we set strict upper limits on the X-ray luminosity of any
undetected point sources, and we exclude the presence of a neutron star
associated with W49B. We conclude that the morphological, spectral, and
environmental characteristics of W49B are indicative of a bipolar Type Ib/Ic SN
origin, making it the first of its kind to be discovered in the Milky Way.
