Lucius Arturius Castus entered military service as a Centurion in 158 AD, and rose in rank to Primus Pilus by 177 AD, 58 rank levels.  He served during Caesar Antoninus Pius and was originally assigned to Syria.  In 166 AD, he was in the Legion of II Adutrix under Caesar Marcus Aurelius and was stationed in the area of present day Budapest, where he fought against and later worked with the Sarmatians.

Out of the original 8,000 Sarmatian Cavalry, only 5,500 survived.  The Sarmatian Knights were the horsemen of the region and lived in the plains between the Black Sea and the Caspian Sea.

In 170 AD, Arturius was stationed in Potassia in Dacia which is modern Turda in the region of present time's Transylvania.  He was assigned to the V Macedonica.  In 173 AD he earned the rank of Primus Pilus.  During the time Caesar Marcus Aurelius conscripted the 5,500 Sarmatian Cavalry that survived and sent them to Britain in 175 AD.  Lucius Arturius Castus was also transferred to the VI Legion Victrix in 177 AD where he was in charge of the Sarmatian Cavalry at Bremetennacum as a Fort Commander.  The Fort lies near Eboracum which is present day York.

In 180-185 AD, the Picts invaded Britain and the Roman Legions suffered heavy losses.  It was known as the Caledonian Invasion.  The Praetorium including the Sarmatians held Hadrian's Wall.  Lucius Arturius Castus was promoted to Praefectus (Fort Commander) and established an outpost fort called Caerleon, known by the Welsh as Camelot.