The imperial radius of action is the radius within which an empire can wage war. Besides the radius of action, the radius of direct rule (the area directly governed) and the radius of influence (the area beyond the radius of action where a given empire has some influence or impact) are important for our understanding of imperial expansion. While the radius of action of modern empires is truly global, this was not the case with ancient kingdoms and empires. Their radius of action was limited by technology and organization. The speed of troops and information, the limits of logistics, and limitations regarding the campaign season, mostly determined by agricultural patterns before the establishment of a standing army, limit the theoretically possible expansion of empires.

The rise of the first empires was based on a sophisticated set of technical and organizational abilities that deserve further study. Due to a lack of sources for many empires, a comparative approach will be helpful. While the conquests of these empires are historical facts, based on abundant evidence, the source situation for the abilities that made these conquests possible is often meager. An analysis of the radius of action and the measures implemented to enhance it enables us to deepen our understanding of the dynamics of empires. Since historical comparison is an essential method to unravel similarities and differences, a double focus on developments in the ancient Near East on the one hand, and in ancient China and South Asia on the other hand, may promise entirely new insights into imperial structures and their interaction with the surrounding territories.

In the framework of this work package, one round table (October 2024 in Tsukuba) and two workshops (Bucharest, October 2024 and Tsukuba, March 2025) have already taken place. The Tsukuba Workshops were intended to gather data, compare the expansion of various empires and to test our model and develop it further. A larger workshop is planned for May 2026 in Innsbruck.