My 3yo

[raresquirrel]

HELP!
I have a very strong willed 3yo who is completely able to resist anything he doesn't want to happen/be done to him. Except when it comes to some of his friends.
He allows them to snatch things from him, puts up no resistance when they hit, pull or charge at him. Which wouldn't maybe be so bad but for the fact that when this happens he looks for me (sometime even calling my name) and then cries.
As a mum its painful to see but I also know I cannot interfere with every battle or disagreement he has with friends, though I do of course offer hugs and support when needed.
Its also difficult as in most instances the other parents are there and even when they do encourage their children to apologise it can happen again just a few minutes later. The parents are on the whole friends too so I don't want to just change our social circles because of this.
I want to bring my child up with a none violent approach to being bullied but I feel a bit stuck as to what to say to him to help and for him not be a victim in these situations.
I'm really looking for some tips and advise please. He is an only child and I have recognised than many of these peers have siblings, which of course could accommodate their assertiveness.
All this considered I'm really looking for ways to talk to him about standing up for his self and for him maybe let his fiends know he doesn't want them to do this to him.