Which section of a fire spreads directly into the wind or downslope, making it the slowest spreading portion?

The rear of a fire refers to the section that is opposite to the head, which is the leading edge of the fire spreading forward. This area is less influenced by wind and topography, resulting in a slower spread compared to other sections. The rear does not receive the same amount of fresh fuel, and the flames are typically less vigorous because they are not advancing into the driving forces like wind or topography that affect the fire's movement.

In contrast, the head of the fire experiences the highest rate of spread as it moves into wind and upslope, which can intensify the fire. The flanks of a fire may also spread rapidly but are generally more influenced by lateral winds and terrain, whereas fingers of a fire represent extensions that can also spread quickly but are not indicative of the slowest section. This distinction clearly identifies the rear of a fire as the slowest spreading part due to its position and the absence of strong driving forces.