The progression from early Christian art to Byzantine art occurred under the rule of **Justinian**.
Explanation:
1. **Justinian I** was a Byzantine emperor who ruled from 527 to 565 AD.
2. During his reign, there was a significant transformation in art from the early Christian style to what is now known as Byzantine art.
3. Early Christian art was characterized by its simple and symbolic representations, while Byzantine art became more elaborate, iconic, and focused on conveying divine majesty and power.
4. Justinian's rule marked a period of artistic flourishing known for the construction of grand churches like the Hagia Sophia, which showcased the intricate mosaics and iconic representations that are hallmarks of Byzantine art.
5. Therefore, Justinian's era played a crucial role in shaping the development of Byzantine art as it evolved from early Christian artistic traditions.
