How do you safely handle a horse that kicks at other horses when being led near them?

A horse that kicks at other horses when being led in close proximity is a serious safety problem — the risk is not just to the other horses but to the handlers and bystanders between the horses when the kick lands or is attempted. Clinton Anderson addresses this specifically because it is a common show environment and trail ride problem. Anderson's first observation is that a horse being led that kicks at other horses is a horse whose attention is on the other horse rather than on the handler. The root cause is insufficient leadership and insufficient focus on the handler. A horse that is fully engaged with its handler — listening for direction, yielding to requests, anticipating the next communication — does not have the mental bandwidth to be running an aggression sequence toward a neighboring horse at the same time. His solution begins not with the proximity situation but with reinforcing attention and leading protocol away from other horses. The horse is put back through leading basics until it walks correctly at the handler's shoulder, yields instantly when bumped, and maintains attention on the handler through direction changes and transitions. Only when these responses are confirmed at high quality does Anderson reintroduce the horse to situations with other horses nearby. In the proximity situation itself, Anderson teaches keeping the kicking horse's attention redirected continuously — not allowing it to get its hindquarters aimed at the other horse by maintaining forward direction, using frequent direction changes, and bumping the lead rope the moment the horse's attention fixes on the other horse rather than waiting for the kick setup to develop. Parelli adds the Friendly Game component: a horse that has been extensively desensitized to other horses approaching, including horses that squeal, that pin ears, and that make sudden movements, has a higher threshold for the situations that trigger kicking. The horse that has been exposed to many horses in many contexts in controlled situations is less reactive when those situations arise unexpectedly.