They don't like to make mistakes. Do this when you are ready. Young children go through four stages as they learn to defend their territory. The first stage is simply hitting or grabbing to get what they need. The second stage is the use of verbal aggression-words as power.
Older preschoolers learn to collect allies.
They learn how to gang up on each other. When you need to, set some rules about these actions, but remember your child is handling situations the best she can with limited experience. Handling things awkwardly is better for a child than not handling them at all. Children ages three, four, and five break rules regularly and can be quite difficult to live with at times, but their rule breaking is only the first step toward rule keeping and rule making, which will become important developmental tasks when they are ages six to twelve. Because of frequent rule breaking, parents often wonder if they will have control of their preschoolers in an emergency.