Final answer:
Empress Irene's time as ruler is not detailed in the provided context, but the Byzantine Empire faced external threats and internal challenges which impacted its stability and longevity. Diplomacy played a crucial role, though the later period saw a decline in military and economic power, eventually leading to the fall of Constantinople in 1453.
Step-by-step explanation:
The leadership of Empress Irene had a significant impact on the Byzantine Empire. Although the question directly mentions Irene, the provided reference materials do not go into detail about her reign specifically; hence, a general overview of the Byzantine leadership and events surrounding her time will set a context.
Under preceding emperors, like Leo the Isaurian, themes-recruited soldiers defended Constantinople and secured Anatolia from Arab threats. The latter period, particularly after the Macedonian dynasty, saw the empire's expansion and the Macedonian Renaissance's cultural flourish. However, following this, successive emperors faced military and economic decline, political instability, and a loss of territorial control.
Despite facing numerous external threats and a decline in power over the centuries, Byzantium's diplomacy and intelligence gathering, such as through the 'Bureau of Barbarians', were pivotal in maintaining stability. Unfortunately, internal challenges such as the power of the dynatoi and less competent rulers also weakened the empire, ultimately culminating in the fall of Constantinople in 1453.