Which invaders attacked the roman empire and caused it to weaken

Germanic tribes -- especially the Visigoths -- attacked the Roman empire and caused it to weaken.

There had been ongoing migration of Germanic tribes into Roman empire territory, that had a gradual weakening effect on the empire.  The western tribes consisted of groups such as the Alamanni, Franks, Angles, and Saxons.  There was also a large group of Germanic tribes known as the Goths.  We speak of the Visigoths and Ostrogoths do distinguish between the western and eastern Goths.  The Visigoths (western Goths) invaded the Roman Empire, and defeated Roman armies at the Battle of Adrianople in 378.  Later, the Visigoths even invaded Italy and sacked the city of Rome in 410.  So I suspect the answer your question is primarily looking for is the Visigoths.

a.tensions between the colonial elites and the backcountry men of virginia.

one of the main reasons was definitely slavery. back in 1861, republican abraham lincoln was elected and ended up being a major influence in the slavery business. slavery greatly affected the texas economy because back in 1845 during the annexation of texas, slaves became a big part of the texas population. many texans that were in favor of the secession influenced groups through party ties.