Steven Runciman, a renowned British historian, is best known for his works on the Crusades, but he also made significant contributions to the study of the Balkans. His major works related to the Balkans include:

1. "The Fall of Constantinople 1453" - This book, while primarily focused on the fall of the Byzantine Empire, provides important insights into the historical context of the Balkans during this period.

2. "The First Bulgarian Empire" - In this work, Runciman explores the history of the Bulgarian Empire, which played a crucial role in the medieval history of the Balkans.

3. "The Medieval Manichee: A Study of the Christian Dualist Heresy" - Although this book covers a broader topic, it includes discussions on the Bogomils, a sect that originated in the Balkans and had a significant impact on the region's religious history.

These works reflect Runciman's deep interest in the complex history of the Balkans and his ability to weave together the intricate narratives of the region's past.