The change in breastplates and helmets contribute to decline of the Roman Empire by weakening the the military. It weaken them because the removal of it promote laziness and negligence of training and the such. It also removes the protection against ranged weapons which caused many casualties.
The correct answer to this open question is the following.
The change in breastplates and helmets contributed to the decline of Rome in that it made the military mean softer; indeed it weakened the army of the once feared Roman Empire.
The armor and helmets were heavier and soldiers had to be more tough and physical. But they were gone -probably the Empire wanted to save money- soldiers appeared to show less character and fierceness. With less protection, there were more dead soldiers on the battlefield.
Other reasons for the decline of the Roman Empire were the invasion of the Barbaric tribes, too much territory to control, government corruption, and economic problems.
What did Soviet leaders expect would happen to communism and capitalism over time? Overtime, Soviet leaders expected a communist utopia of social justice and economic equality
