Wildland fire involves both chemical and physical processes. When wildland fuel burns, its stored chemical energy is converted to thermal energy or heat through complex chemical reactions. But for the reactions to be started, heat must be physically transferred from a firebrand to the fuel, and heat transfer to unburned fuel must continue if the fire is to keep on burning and spreading. Control and extinguishment of a wildland fire hinges upon the interruption of the chemical reactions. And about the only way we have of doing this is to reduce or eliminate heat transfer. In earlier publications, we explored the nature of heat and the process of heat transfer by conduction. In the following discussion we will look at the combustion process and the part that heat conduction plays in it, and how heat transfer by conduction can be checked in fire control operations. The level of difficulty of the treatment of topics in these publications varies, as signaled by the color of the cover: the blue cover group is generally elementary and the yellow cover group is intermediate.