  We review Galactic halo formation theories and supporting evidence, in
particular kinematics and detailed chemical abundances of stars in some
relevant globular clusters as well as Local Group dwarf galaxies. Outer halo
red HB clusters tend to have large eccentricities and inhabit the area
populated by dwarf spheroidal stars, favoring an extraGalactic origin. Old
globulars show the full range of eccentricities, while younger ones seem to
have preferentially high eccentricities, again hinting at their extraGalactic
origin. We compare detailed abundances of a variety of elements between the
halo and all dwarf galaxies studied to date, including both dwarf spheroidals
and irregulars. The salient feature is that halo abundances are essentially
unique. In particular, the general alpha vs. [Fe/H] pattern of 12 of the 13
galaxies studied are similar to each other and very different from the Milky
Way. Sagittarius appears to be the only possible exception. It appears very
unlikely that a significant fraction of the metal-rich halo could have come
from disrupted dwarf galaxies of low mass. However, at least some of the
metal-poor halo may have come from typical dwarfs, and a portion of the
intermediate metallicity halo may have come from very massive systems. The
chemical differences between the dwarfs and the halo are due to a combination
of a low star formation efficiency and a high galactic wind efficiency in the
former. The formation problem may be solved if the majority of halo stars
formed within a few, very massive satellites accreted very early. However, any
such satellites must either be accreted MUCH earlier than postulated, before
the onset of SNe Ia , or star formation must be prevented to occur in them
until only shortly before they are accreted.
