Chained. The reason why these children were not be able to walk faster was because their feet and hands were chained.
Iris couldn't see it from afar, because the chain was very thin, but it was very tight, it bit against their skin. More so, with this dark sky, it was hard to see.
From closer look, you would be able to tell that the length of the chain between their ankles were enough for them to take a small step, while their hands were tied together.
Young children were crying because they were hungry, thirsty, tired and in pain. Those, who were slightly older tried to comfort them, but Lou's men raised their whip, ready to lash them.
Iris was stunned, her body stiffed when she saw the whip. It reminded her of how Mason used to do that to her, but a muffled cry from the child snapped her out of it when the whip left a deep wound on his skin and blood oozed out.