This document summarizes a Harvard Business School study on why successful companies fail to adapt to changes in their environment. It provides examples of Firestone Tire & Rubber and Laura Ashley, both leading companies that failed to respond appropriately to major shifts. The concept of "active inertia" is introduced, where companies continue established patterns of behavior despite dramatic changes. Key hallmarks of active inertia include strategic frames becoming blinders, processes hardening into routines, relationships turning into shackles, and values hardening into dogmas. Both case studies illustrate how formerly successful companies were hindered by active inertia when they needed to transform their strategies, operations, and cultures.