Afghanistan is a land of vast deserts, high mountains and a million caves. The Afghans have long used the many caves for shelter and storing stuff. During wartime, the caves are a good place to hide fighters, as well as caches of food and ammunition. When the Russians fought Afghans during the 1980s, they had a terrible time with Afghans in caves. The Afghans knew where the caves were, which ones had two entrances and used this knowledge to use the caves for ambushes and combat in general. Caves are difficult to deal with, as they usually have small openings, and are often deep enough so the Afghans can go deep and avoid Russian fire power. After the Afghan war, the Russians came up with a solution to the caves problem; portable FAE (Fuel Air Explosive) weapons. The Russian Shmel (Bumble Bee) is a rocket propelled warhead fired from a launcher similar to that used by their RPGs (anti-tank rocket launcher). The RPO-A (Infantry Rocket Flame Thrower) is used against caves and bunkers, as well as armored vehicles. The RPO-Z is used against buildings and troops in the open. The basic principle of FAE is a container of gasoline like fuel that is spread (by compressed gas) to form a mist cloud of fuel. A detonator than ignites the cloud and causes a huge explosion. The effect is like a nuclear weapon, for there is enormous pressure and a lot of flame. All the oxygen is also used up. So if you aren't crushed or burned, you die from lack of oxygen. The Russians have developed a new fuel that is better able to seep into wherever air can go before detonating. In a cave, everyone dies. Even armored vehicles are vulnerable because some of the fuel sometimes seeps into the vehicle and starts fires when it explodes. If US troops do end up fighting inside Afghanistan, Shmel's can be obtained from Russia, which is selling RPOs to anyone with the cash.