VALENS 364 - 378 AD : FLAVIVS IVLIVS VALENS AVGVSTVS BORN 328 AD, CIBALAE, PANNONIA, RULE 14YEARS 28 MARCH 365 A.D. – 9 AUGUST 378 A.D. Appointed co-Augustus for the east by Valentinian I his brother Killed in Battle of Adrianople against the Goths.
The late Roman legion used round shields because the Roman state didn't have the money to train the soldiers to work as an organized fighting machine like the early legion was. Instead the late legion was a militia and hence had to use round shields because round shields are better in individual combat.
Roman legionaries attacking Visigothic wagons at the Battle of Adrianople