In the first century AD, Jews lived across the Roman Empire in relative harmony. Later along Jews had been banished from Rome in 139 BC, again in 19 AD and during the reign of Claudius.
I tried!!
Because of imperialism, countries now had access to colonies. When the war started, they were able to equip their colonies to fight for their side. This led to higher tensions and increased involvement in the war.
I belive the answer is Feudalism. It was used in Medievaltimes.