<P> The imperial period of Rome lasted approximately 1,500 years compared to the 500 years of the Republican era . The first two centuries of the empire 's existence were a period of unprecedented political stability and prosperity known as the Pax Romana , or `` Roman Peace '' . Following Octavian 's victory , the size of the empire was dramatically increased . After the assassination of Caligula in AD 41 , the Senate briefly considered restoring the republic , but the Praetorian Guard proclaimed Claudius emperor instead . Under Claudius , the empire invaded Britannia , its first major expansion since Augustus . After Claudius ' successor , Nero , committed suicide in AD 68 , the empire suffered a series of brief civil wars , as well as a concurrent major rebellion in Judea , during which four different legionary generals were proclaimed emperor . Vespasian emerged triumphant in AD 69 , establishing the Flavian dynasty , before being succeeded by his son Titus , who opened the Colosseum shortly after the eruption of Mount Vesuvius . His short reign was followed by the long reign of his brother Domitian , who was eventually assassinated . The Senate then appointed the first of the Five Good Emperors . The empire reached its greatest extent under Trajan , the second in this line . </P>
<P> The imperial period of Rome lasted approximately 1,500 years compared to the 500 years of the Republican era . The first two centuries of the empire 's existence were a period of unprecedented political stability and prosperity known as the Pax Romana , or `` Roman Peace '' . Following Octavian 's victory , the size of the empire was dramatically increased . After the assassination of Caligula in AD 41 , the Senate briefly considered restoring the republic , but the Praetorian Guard proclaimed Claudius emperor instead . Under Claudius , the empire invaded Britannia , its first major expansion since Augustus . After Claudius ' successor , Nero , committed suicide in AD 68 , the empire suffered a series of brief civil wars , as well as a concurrent major rebellion in Judea , during which four different legionary generals were proclaimed emperor . Vespasian emerged triumphant in AD 69 , establishing the Flavian dynasty , before being succeeded by his son Titus , who opened the Colosseum shortly after the eruption of Mount Vesuvius . His short reign was followed by the long reign of his brother Domitian , who was eventually assassinated . The Senate then appointed the first of the Five Good Emperors . The empire reached its greatest extent under Trajan , the second in this line . </P>
when did the roman empire reach its greatest extent
when did the roman empire reach its greatest extent
under Trajan
under Trajan