The decline of Byzantine Empire and Western Roman Empire are similar in which both had military decline that affected the overall decline. In the Byzantine Empire, a major factor in the decline may have been the disintegration of its traditional military system, the “theme” system. As one of the main strengths of the Byzantine Empire, the theme system was never replaced by a viable long-term alternative. This led to decline because Constantinople was taken over by 1204 after having a weak military. In the Western Roman Empire, Germanic mercenaries were being put into ranks in legions thus leading to a more “barbaric” army since they were more loyal to the commanders than the government itself. Just like the Western Roman Empire, the Byzantine Empire had small civil wars that had occurred which played small parts in the decline of the empire. Both of the Empires also had long and drawn out declines. The Byzantine Empire had faced many conflicts before it fell, and so did the Western Roman Empire; as both processes took centuries. The emperors of late third century and early fourth century had divided the army into borders; this made the troops to become the soldier-farmer and has declined their efficiency. These emperors also allowed barbarians into the army, which decreases the army’s fighting efficiency. The weakness of border troops meant that the emperors needed more mobile troops. Hence they had expanded their army. This expansion had paved the way for the recruitment of barbarians into the army. By AD369 the Roman Empire was beginning to crumble for the following reasons: The Government was running out of money. The people had to pay very high taxes - up to a third of their money. As in the Byzantine there was the free peasantry upon which the government depended for taxes and recruits. When the empire had been under constant attack, land had been a poor investment. In these Emperors there was a constant battle as the nobles tried to get these lands and ensure the peasants. The government, seeing the free peasantry as the backbone of its economy and defense, did what it could to defend them. Outsiders, especially Slavs and Armenians, accepted similar terms. Over time hereditary military leaders developed regional power and displaced better-educated aristocrats. The empire politically and economically depended upon Constantinople's control of the countryside. Peasants supplied the food and provided most tax revenues. When it came to the lack of money in their economy because both of their governments were relied upon the taxes and if there was no move of work from the people then the government would not get a lot of money and that’s why they began to required higher taxes. The financial problem faced by the Empire, As the Roman Empire divided into Eastern and Western part, the Western part had fewer of the wealthy provinces, which decreased the amount of tax collected. The West had longer borders to defend and had to have a greater army, but paying for enough army was the problem. The civil war during the fourth and fifth centuries also drained all the resources of the Empire hence made its collapse inevitable.
While the Western Roman Empire was facing many rebellions due to unhappy civilians the Byzantine Empire was struggling with the rise of Islam. The Arabs had found a new desire to conquer and waged “Byzantine-Arab Wars” which were a series of wars between the Arab Caliphates and the East Roman or Byzantine Empire between the 7th and 12th century AD. Another internal problem consisted of an economic slowdown for the Western Roman Empire. Some Roman landowners were even being expelled and their lands confiscated, while the Western Rome was facing economic problems, the Byzantine Empire was going through the hardship of participating in the Crusades. This created a rift between the army and the civilians of the country, which was the immediate cause of collapse of the Roman Empire. The lack of circulating currency in the western part of the Roman Empire was the root cause of economic deterioration. There was also massive trade deficit with the Eastern part of the Empire, which also helps to decrease the economic growth of the Western part of the Empire. The Crusades was another outside pressure that was added on to the vast amount of pressures they already had. The Crusades had assisted the weakening of the Byzantine Empire. The numerous divisions in the Roman Empire had also contributed to the fall of the Western Roman Empire. The government was soon becoming unstable and was filled with corrupt leaders. Even though the Western Roman Empire was facing harsh internal problems, the Byzantine Empire was still being pressured by outside forces; this time, the rise of the Ottomans. The arrival of the Seljuk Turks led to the rise of the Ottomans. Soon the Ottomans began t gain support in the regions in Asia Minor. This eventually led to the Ottomans having a successful siege over Constantinople. This event marked the end of the millennium-long political independence the Byzantine Empire had.
The decline of the Byzantine Empire was a process similar to the decline of the Western Roman Empire in that inner politics and military were becoming a huge factor in the decline of these empires. They had also differed by having certain pressures affecting the decline of these empires. While the Byzantine Empire was facing external pressures, the Western Roman Empire was facing internal pressures. The Byzantine Empire, once part of the greater Roman Empire, continued flourishing from an eastern Mediterranean base after Roman decline. Although it inherited and continued some of Rome’s heritage, the eastern Mediterranean state developed its own form of civilization.