By "it" I assume you mean uke's motion. Perhaps an analogy will help. Imagine a horse, a cart, a carrot, some string and a stick.Now in order to get the horse to move the cart I have to hang the carrot from the stick using the string and dangle it in front of the his nose. The horse, though, has a mind of his own and will often change direction with no warning. If he loses sight of the carrot he will stop.In order to keep the horse moving I have to make sure he can always see the carrot so I have to simultaneously stay slightly ahead of his motion (lead) while following where he goes.
It seems to me that this will only work so long as uke decides to do what you want, on his own, in a dojo. This fails when you're actually fighting someone smarter than a horse. As for myself, I prefer to be in a position where the person has no choice but to move with me (not me moving with him), using connection.