Chase, the primary factor that enabled the Romans to conquer most of the known world was their development of what is generally agreed to be the world's first professional army.

The Romans developed just about every aspect of modern armies, except for air power. Soldiers enlisted for a period of 20 years, went through a period of basic training, then for the rest of their service when they weren't campaigning they trained, trained, trained. The Romans had specialized combat and combat support arms, including infantry, archers, slingers, cavalry, "artillery" (ballistas and catapaults), marines, engineers, military police, medics, quartermasters, military intelligence, etc., etc.

They had the equivalent of today's Command and General Staff College, where after-action reports and captured weapons were studied to keep abreast of new enemy tactics and capabilities, where new doctrine was developed, and changes in military training were promulgated. This enabled the Roman army to keep ahead of the curve.

They had their version of West Point, where cadets and promising soldiers were trained to be officers.

They developed a system of ranks, based on the number of men to be supervised and lead -- including what we would call non-commissioned officers -- and there were no social or class restrictions on advancing up to the highest ranks in the army. Roman society had a definite caste and class structure, but they were very pragmatic when it came to the army. Skill counted more than class.

Roman "regiments" (or legions) had a lineage and heritage just like modern military regiments, but of course theirs went back a lot further. By the time the last vestiges of the Roman Empire fell -- there were legions which could trace their lineage back several hundred years. Legions had "colors" (in the form of gold or silver eagle), and were awarded battle honors.

Soldiers were paid regular salaries, received medical treatment from army surgeons and in army hospitals, were provided with disability retirement, and at the end of their military service received a pension and land.

Thousands of surviving documents show that a Roman legion or garrison had muster rolls, work detail rosters, discharge certificates, furlough papers, requisitions, general orders, and all the other red tape that any self-respecting military bureaucracy needs.

They developed some unique weapons systems, such as spears with break-away tips, so that the enemy couldn't throw them back. Pretty nifty idea.

They developed the science of seige warfare to a high art. There is no record of a single unsuccessful Roman seige. In some cases it took more than a year to conquer a city, but a soldier serving a 20-year enlistment has all the time in the world. Once the Romans got after you, it was all over but the shouting.

On those occasions when the Romans suffered a defeat in the field, it was almost always due to stupidity on the part of the commander -- deviating from tried and true Roman strategy.

I'll tell you, Chase, the study of the Roman military is just like reading about a modern army. Very interesting stuff. It's amazing how much modern armies have modeled themselves on the Roman tradition.