In an attempt to eliminate the 'growth phase' controversy a unified phenomenological model of substorm sequences is presented by taking recent findings into account. The following three fundamental requirements are important in synthesizing the vast amount of ground-based and satellite observations: (1) substorms can occur regardless of the direction of the IMF (interplanetary magnetic field) except during a large prolonged northward IMF which yields a 'ground' state of the magnetosphere, (2) substorm occurrence probability increases with an increase of available energy in the magnetotail which exceeds the ground state energy, and (3) substorms are, in general, intense when the available energy is large.