protecting caravans

[Mellmak]

Hey
What i find a little iritating is that i got my army of treants that i use to transport stuff and its constantly getting attacked. They cannot defend themselves. Im using treants only to increase efficiency. They have some combat value but they cant attack units (lol) .There should be a feature somewhere that helps defending those. Like if i have a separate army with it it should be able to defend it. I in general feel that treants and bolt throwers are a lackluster (at least when i played last time )