Byzantine EmpireThe Byzantine Empire, also referred to as the Eastern Roman Empire, was the continuation of the Roman Empire primarily in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constantinople. It survived the fall of the Western Roman Empire in the 5th century AD and continued to exist until the fall of Constantinople to the Ottoman Empire in 1453. During most of its existence, the empire remained the most powerful economic, cultural, and military force in the Mediterranean world.
Roman armyThe Roman army (Latin: exercitus Romanus) was the armed forces deployed by the Romans throughout the duration of Ancient Rome, from the Roman Kingdom (753 BC–509 BC) to the Roman Republic (509 BC–27 BC) and the Roman Empire (27 BC–476 AD), and its medieval continuation, the Eastern Roman Empire. It is thus a term that may span approximately 2,205 years (753 BC–1453 AD), during which the Roman armed forces underwent numerous permutations in size, composition, organisation, equipment and tactics, while conserving a core of lasting traditions.
Roman–Persian WarsThe Roman–Persian Wars, also known as the Roman–Iranian Wars, were a series of conflicts between states of the Greco-Roman world and two successive Iranian empires: the Parthian and the Sasanian. Battles between the Parthian Empire and the Roman Republic began in 54 BC; wars began under the late Republic, and continued through the Roman (later Eastern Roman (Byzantine)) and Sasanian empires. A plethora of vassal kingdoms and allied nomadic nations in the form of buffer states and proxies also played a role.
Rashidun CaliphateThe Rashidun Caliphate (al-Khilāfah ar-Rāšidah; 632 661) was the first caliphate to succeed the Islamic prophet Muhammad. It was ruled by the first four successive caliphs of Muhammad after his death in 632 CE (11 AH). During its existence, the empire was the most powerful economic, cultural, and military force in West Asia. The caliphate arose following Muhammad’s passing in June 632 and the subsequent debate over the succession to his leadership.