The soldiers likely died in the Battle of Mursa that took place around 260 CE. Credit: PLOS One Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent every weekday. Among its many feats, Rome featured one of history’s most organized and successful military forces. Its organization and deployment helped solidify the empire’s centuries-long reign across the Mediterranean, Western Asia, North Africa, and Europe. In Croatia, archaeologists have discovered a mass grave dating back to the third century CE that indicates another key to Roman military strength: the diversity of its soldiers. Their findings are detailed in a...