  We describe and report progress on the joint U.S. and German campaign to map
the X-ray emission from the entire Cygnus Loop supernova remnant with the ROSAT
High Resolution Imager. The Cygnus Loop is the prototype for a supernova
remnant that is dominated by interactions with the interstellar medium and
supplies fundamental physical information on this basic mechanism for shaping
the interstellar medium. The global view that these high-resolution
observations provide emphasizes the inhomogeneity of the interstellar medium
and the pivotal nature of cloud-blast wave interactions in determining the
X-ray morphology of the supernova remnant. While investigating the details of
the evolution of the blast wave, we also describe the interstellar medium in
the vicinity of the Cygnus Loop, which the progenitor star has processed.
Although we do not expect the X-ray observations to be complete until September
1997, the incomplete data combined with deep H$\alpha$ images provide
definitive evidence that the Cygnus Loop was formed by an explosion within a
preexisting cavity.
