Troops

Hi all. I am looking to convert my bowmen to longbowmen, is there any way I can disband my bowmen or do I have to suicide them? Is this a good idea in general or am I misunderstanding troops? What would be my best way to do this?

Thanks

Suicide runs are the only way

and I'm not missing something that would make me want to keep the bowmen and not replace them with longbowmen?