Roman Military Technology

Militaries are known throughout the world. It's usual for most countries and societies to have them but where did the idea of having a large and tactical military force come from? Where did the ideas for the technology they now have stem from? That would be the first largest and most technologically advanced military to make history; The Romans. From their swords to large war forts they were very much advanced when it came to having a technological advantage over those who stood no match against them.