Why did Diocletian divide the Roman provinces into smaller units?

Diocletian divided the Roman provinces into smaller units primarily to improve administrative efficiency and security. By fragmenting the provinces, he aimed to bring governors into closer proximity to the populations they administered, thereby ensuring more effective oversight.1

Furthermore, this reorganization served a strategic political purpose: by reducing the size of the territories governed by individual officials, Diocletian diminished their territorial strength and influence, which helped prevent potential revolts and centralized power under his own authority. While some contemporary accounts, such as those by Lactantius, suggested the division was intended to make the emperor more feared, the reforms were fundamentally designed to stabilize the empire through increased bureaucratic control and a more manageable administrative structure.1