What they did to fight for many hours/days?

[Nicholas Gaukroger]

But they did fight all day in some cases......There are instances in the 69 civil war mentioned.

I thought a fair bit of that was dodging artillery and taking cover in vineyards and orchards (ref. Cremona)? It still doesn't exclude troop rotation and rests.

True, But there were periods of quite intense fighting as well, so it would support the idea of rests, I would think. As opposed to a short sharb battle deciding the day. There was some hard fighting on some narrow roads surrounded by vineyards I recall?

Short, sharp, abttles were a feature of Greek warfare and not Roman ones which appear to have been much longer (Sabin's "Lost Battles" book covers this to some degree).

However, it is pretty much physically impossible that even these long battles involved prolonged periods of hand to hand fighting by any individual part of the battle line - the human body and psyche just can't handle it. So long battles must have contained major period of less intesive activity and/or had action in different parts of the field.

BTW there is an interesting analysis by Zhmodikov on the amount of time Roman armies spent in missile exchanges rather than hand to hand fighting - a lot more than I thought thats for sure hock:

[Gaius Julius Caesar]

Yes, sorry we are going a bit off the track here. My apologies.