Finally got around to reading this book - but only about 25% read so far. Some good stuff in here with a good description of Roman tactics and how they changed through history. I'm upto the Mid Republican Romans at present.
Found out nore about the checkerboard formation - it appears that it allowed the Romans to move about the battlefield quicker than trying to keep a long line of troops together (especially over broken ground) as well as give them more flexibility when battle was joined. Apparently, the same idea was used by other forces, including the Carthaginians, to speed up deployment.
The hastati and principes were typically armed with two pila - with an effective rang of just 30 metres (and often used at much closer range). Polybius stated that the pila were two different weights - one considerably heavier than the other, presumably used just before the lines clashed for maximum impact. These were designed specifically for armour piercing. Bad news for a bare-chested Gaul! If caught by a shield the barbed head would prevent it from being pulled out and so would badly hinder the recipient. Often the shields had to be abandoned (also bad news!).
What does come across is the level of professionalism in the army - in contrast to many of the enemies they fought. For example, each camp set up at night was done so according to strict rules and regulations. Roman camps would always be exactly the same - laid out in a strict pattern. It was sighting a Roman camp for the first time that Pyrrus understood that he was facing not barbarians but a well ordered and disciplined enemy.
I also found out that Hadrian's Wall was not the furthest point of the Roman occupation of Britain. There were a line of forts along both main roads up the length of Scotland and a further wall (the Antonine Wall) which appears to be along the line of Glasgow to Edinburgh - again with forts further north than that. But they eventually retired behind Hadrian's Wall and (as the Empire collapsed) gave it up altogether.
The Roman cavalry (in Mid Republican Rome) was weak primarily because of numbers - a typical legion had only about 300 horse. Which explains how Hannibal's cavalry always seemed to knock them off pretty quickly.
More interesting stuff as I get through it.