What economic strategy entails bringing together former competitors under a single corporate umbrella?

The concept of bringing together former competitors under a single corporate umbrella is best described by horizontal integration. This strategy involves acquiring or merging with companies that operate at the same level in an industry, effectively consolidating market share and reducing competition. A historical example of this can be seen in the business practices of John D. Rockefeller, who used horizontal integration to dominate the oil industry by purchasing rival refineries.

In contrast, vertical integration refers to the consolidation of entities involved in different stages of production or distribution within the same industry. Conglomerate integration refers to the merging of companies in unrelated industries, thereby diversifying business operations. A monopolistic strategy would describe the conditions or practices that aim to establish a monopoly, but this is not a specific economic strategy focused on competition consolidation like horizontal integration is.