Short answer, like a pack string, tie one to the other using a short rope.
Long answer:
Many years ago I rode with a man who was a former Cavalry Officer --he’d been in his late teens when he joined the military prior to WWII --might have been as early as 1930s. He rode cavalry horses at Ft. Leavenworth KS under the command of old time cavalry officers and instructors. Ultimately he was a tank commander in WWII (under Patton), and became the director of horsemanship at a military academy where there were 135 horses --I believe it was the last bastion of horse mounted cavalry.
The stable when he ran it was “old school” cavalry --135 tie stalls, horses brought in, each tied for the night in his/her stall, taken out the next day by cadets, ridden 2 h in the AM and 2 h in the PM and given time to graze in hand (again by the cadets) for two hours. On school holidays, the horses were turned out into the 500 acre pasture.
I asked your question --how did the 5 full time hired stablemen move the horses down the paved road to the pasture –
It was the “cavalry way” --found out that only rarely did the cavalry fight from horseback (horses were too valuable for moving soldiers quickly from place to place) --instead, every 5 horses connected together (short strap, one bridle/halter --under chin to cheek ring) to the horse beside it as the soldiers dismounted. The 5th man led the 4 tied together horses behind the firing line and waited until ordered back to pick up the first 4men. . .
Yes there were sabre charges and cavalry charges, but according to my friend, these were last ditch efforts because the horses would die in the effort going against guns and sabers of the enemy. .
When my kid played polo, I watched the grooms in the AM exercise up to 10 horses at a time, all attached the same way --groom rode on horse, and all the others were “daisy chained” halter to halter, under chin ring to cheek ring. It was fun to watch as the polo grooms would walk and trot their horses around the track .
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oops