The Romans were highly successful in war due to their effective weapons and tactical formations. They had armor like the lorica segmentata and helmets like the cassis to protect soldiers. Offensive weapons included the short gladius sword, powerful pilum javelins, and mounted ballistae and onager artillery. Defensive formations were used like the tortoise and wedge to minimize casualties and break enemy lines. Together, these weapons and tactical innovations allowed the Roman army to dominate opponents.