  The goal of this survey is to study the formation and evolution of the Milky
Way halo to deduce its assembly history and the 3D distribution of mass in the
Milky Way. The combination of multi-band photometry, Gaia proper motion and
parallax data, and radial velocities and the metallicity and elemental
abundances obtained from low-resolution spectra of halo giants with 4MOST, will
yield an unprecedented characterisation of the Milky Way halo and its interface
with the thick disc. The survey will produce a volume- and magnitude-limited
complete sample of giant stars in the halo. It will cover at least 10,000
square degrees of high Galactic latitude, and measure line-of-sight velocities
with a precision of 1-2 km/s as well as metallicities to within 0.2 dex.
