  We compare the description of the M-theory form fields via cohomotopy versus
that via integral cohomology. The conditions for lifting the latter to the
former are identified using obstruction theory in the form of Postnikov towers,
where torsion plays a central role. A subset of these conditions is shown to
correspond compatibly to existing consistency conditions, while the rest are
new and point to further consistency requirements for M-theory. Bringing in the
geometry leads to a differential refinement of the Postnikov tower, which
should be of independent interest. This provides another confirmation that
cohomotopy is the proper generalized cohomology theory to describe these
fields.
