This popular phrase goes back at least as far as 1597, when William Shakespeare wrote “Be stirring as the time; be fire with fire; Threaten the threatener and outface the brow of bragging horror” in his play “The Life and Death of King John.” In other words, match aggression with aggression. Meet violence with violence. It all amounts to “an eye for an eye.” When faced with a massive, woodland-consuming storm of flames and ash, your first instinct might not be to apply more fire to the dire situation. But think about it for a second: A fire needs oxygen and fuel, such as leaves and vegetation, to continue raging. Rob the fire of either source of nourishment and you squelch the chemical reaction that produces it. Check out our pass blog, How do Firefighters put out Wildfires? to learn how they do it. Now when faced with an oil-well fire firefighters have been known to remove the oxygen from the equation by detonating a little dynamite. The blast eats up all the local oxygen, leaving nothing to keep the fire going. So fight fire with TNT! When an entire forest is ablaze, however, a different tactic is in order. Firefighters remove the fuel — and what better way to quickly remove combustible underbrush than to carefully set it on fire? This technique is called backfiring. In this strategy, firefighters attempt to halt the advance of a wildfire (or redirect it) by burning up fuel in its path. The burn creates a manmade firebreak, or gap, in combustible material to contain spreading wildfires. Several different fire-spreading gadgets help firefighters pull this off, including forest fire torches or fusses (which work much like a road flare), propane torches and drip torches. But it’s ok, grass and forest fires are a natural occurrence. In a world with no humans, forest fires would still happen, whether due to lightning strikes, sparks from falling rocks, volcanic activity, and the natural spontaneous combustion of organic materials. This is a completely normal part of the ecological cycle. . Some plant species actually depend on fire as part of their reproductive cycle, while others evolved long ago to weather regular wildfires. Sequoia seeds, for example, actually remain dormant until fire breaks down the seeds’ outer coating. As such, a good controlled burn can also aid the environment by stimulating local vegetation. Although it sounds completely metaphorical, fighting fire with fire is a rather practical method used by fire fighters.