26 miles, but the legions didn’t run them, they walked. Our soldiers today carry a lot of weight and can cover that much distance in a day also(would be about 39 miles).
You can fight or you can hump. if you look at the most recient wars Grunts shed the useless and kept what was needed.
Don’t forget, they did that day in and day out, the length of continents. They did it after first breaking...as in rendering unusable by an enemy...camp; and then, at the end of the march, building a new fortified, often palisaded, camp for the night.
Didn’t have MREs, either, though that may be considered a plus by some.