I cannot write the essay for you but I can give you an outline for one. What happened was, was that Rome suffered from a series; lineage of bad emperors who made bad decisions for its armies and bad decisions for its territories. Rome was in a state of decline for that reason. People were not satisfied with the condition Rome was in and this caused a reason for unrest which then caused another source of worry for the emperors. Furthermore, they were increasingly being attacked by foreign invaders first in small skirmishers and later in bigger ones until the fall of the Western Roman Empire.