Captain’s shooting.

Right-click on the defense button in the corner, and in the menu that appears, select "melee" (figure out the meaning based on the context), press OK, and they will attack with their hands. Similarly, for any ranged units, and also for creatures that return to their original position after attacking (like harpies), you can select the option to stay in place after the attack in the same menu. Just remember that this mode remains active, and you need to switch back to another mode when you need different behavior; it doesn't reset automatically.