The physical processes involved in the transfer of energy from the solar wind to the magnetosphere, and release associated with substorms, have been examined in a sequence of Coordinated Data Analysis Workshops (CDAW 6). Magnetic storms of March 22 and 31, 1979, were chosen to study the problem, using a data base from 13 spacecraft and about 130 ground-based magnetometers. This paper describes the March 22 storm, in particular the large, isolated substorm at 1054 UT which followed an interval of magnetic calm. We summarize the observations in the solar wind, in various regions of the magnetosphre, and at the ground, synthesizing these observations into a description of the substorn development. We then give our interpretation of these observations and test their consistency with the reconnection model. The substorm appears to have been generated by a southward turning of the interplanetary magnetic field associated with a current sheet crossing. Models of ionospheric currents derived from ground data show the substorm had three phases of development. During the first phase, a two-celled convection current system developed in the polar cap as synchronous spacecraft on the nightside recorded an increasingly tailike field and the ISEE measurements show that the near-earth plasma sheet thinned. In the second phase, possibly triggered by sudden changes in the solar wind, a one-celled current system was added to the first, enhancing the westward electrojet. During this phase the synchronous orbit field became more dipolar, and the plasma sheet magnetic field turned strongly southward as rapid tailward flow developed soon after expansion onset, suggesting that a neutral line formed in the near-earth plasma sheet with subsequent plasmoid ejection. In the third phase, which occurred after interplanetary magnetic field turned northward, the magnetospheric current system decayed as the plasma sheet expanded and the flow turned earthward. The data from this event support the notion that substorms include two major processes of energy dissipation: one directly driven by the solar wind and one driven by release of energy stored in the geomagnetic tail. The near-tail data suggest that one or more neutral lines formed earthward of the ISSE spacecraft. However, all the signatures of plasma flow and energetic particles can be explained only by postulating a complex series of events. While this reconnection picture represents the interpretations of many of the CDAW 6 participants, it is not a consensus viewpoint.