Invasions of people--many of the groups came as military and fought the Romans as invading forces.
Counterclaim--they were migration patterns as they were attempting to gain access to an empire with advanced trade and education. Migrating to the Roman Empire gave a person or group with extra resources.
American Revolutionary War
Lucius Cornelius Sulla the Roman dictator was the one responsible for the dramatic changer in Roman consitution. Sulla's politics was rather conservative, and Sulla had an objective to strengthen the Roman Senate and reduce the power of the plebeian tribunes. He retired in 79BC.
The differences between the Mughal and the Ottoman Empires is that the Ottomans had a majority Christian region, while the Mughals were ruling over Hindu majority region.
Secondary sources is the right one