The Roman Army
The Romans believed that they were descendants of Mars, the god of war. This may have helped there psyche as they started on the long road to become one of the biggest empires in history and to create an army so strong it would not be matched again for centuries. The Roman army was well trained and the soldiers were full time, just like in Sparta. They ha one profession -- war. Not only was the Roman army well trained it was well led and it also adapted to the situations and environments that it encountered.
Weapons
The weapon that all Roman soldiers carried was called a short sword called a gladius and a sheid or scutum. Each soldier also had a back-up sidearm referred to as a pugio that was a short dagger used in case he lost his main weapon. Along with those soldiers carried spears called pilums that were wooden rods with a metal spike inserted into the end.
Siege Weapons
When placing an enemy under siege the Romans created ingenious weapons that were far ahead of their time. A famous siege engine, the ballista, was essentially a large crossbow used to propel large darts or rocks at enemy walls and defenses. Another one,a catapult called the onager was a torsion based catapult that launched large rocks and boulders at enemy targets. The most famous of all siege engines, the battering ram, or aries was a large wooden pole that was used to break down enemy walls. The weapon often had a ram's head carved or mounted onto the end as a sort of pun. The ram's were often covered with roofs to defend the soldiers from archers and other objects being thrown at them. The battering ram is still used today by some police and military units.
Battle Dress
For battle, Roman soldiers dressed in tunics with leather armor or in chain mail. Centurions generally wore scale armor know as Lorica Segmentata, like shown in the picture. It was strips of metal held together by sturdy leader straps, its design made it a good defense from sword blows. The helmet called a cassis had a plate protruding from the forehead that was designed to prevent any sword blows from penetrating the helmet during combat.