Re: A days journey
Pre 20th century, when infantry really marched to battle, normal speed on a decent road was 2.5 mph (marching 50 minutes and a 10 minute break) and 8 hours the standard time of march per day, so 20 miles per day was normal. Bad terrain would slow you down of course.
With a "forced march" 30 miles a day was plausible, but that exhausts the troops.