Russia has used successful performance of its weapons in Syria and Iraq to revive sales of some older systems. One of the more unique among these revived weapons is the TOS-1A. The “TOS” stands for “heavy flamethrower system” because the TOS-1A only fires rockets equipped with FAE (Fuel Air Explosives) warheads. The TOS-1A is a 45 ton vehicle that uses a T-72 tank chassis with the turret replaced by a box-like launcher for 24 220mm rockets. These come in two sizes, one is 3.3 meters (20.8 feet) long and weighs 173 kg (381 pounds) while the other is 3.7 meters (12.1 feet) long and weighs and 217 kg (478 pounds). The larger rocket has a longer (6,000 meters) range. The TOS-1A is not a direct-fire weapon but the vehicle is meant to get close to the target and is equipped with a laser range finder and computerized fire control system to elevate the launcher to the right angle to put the unguided rocket as close to the target as possible.
The TOS-1A is considered a “chemical weapon” by the Russians while other nations simply consider FAE an exotic, and but in fact FAE has been around since World War II. While FAE can be very effective it is a temperamental type of explosive that is not widely used. FAE is a warhead that first spreads a mist of fuel (gasoline type stuff, or a mixture of other chemicals) and then ignites it. This creates a large, impressive looking, explosion, as well as a powerful blast (called overpressure). The overpressure is powerful enough to set off landmines, as the pressure created on the ground triggers the pressure sensors on anti-personnel and anti-tank mines. This FAE warheads are often used to clear landmines. The effective blast radius of the TOS-1A rocket warhead is over a hundred meters.
FAE has always been tricky to use. If the wind is blowing the wrong way, or the humidity isn’t quite right, the explosion is something of a fizzle. But the Russians have developed new designs for FAE weapons (which they now call "thermobaric weapons") that overcome many of these problems. Current FAE designs use 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. Modern FAE chemicals are 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.
The original TOS-1 was developed in the 1980s and used in combat in Afghanistan in 1988. Apparently it was successful but the Russians were withdrawing and they took their TOS-1s with them. With the collapse of the Soviet Union in 1991 there was little money to build or further develop the TOS-1. At that time there were only about twenty in service. There were used in Chechnya during the 1990s and that was successful enough to revive development. That led to the TOS-1A in 2002 and production has increased since then. Over two hundred TOS-1s (mostly the 1A model) have been ordered. In Syria the Assad forces used some of the older TOS-1s in combat while Iraq bought a dozen TOS-1As which they used extensively in the battle for Mosul. For city fighting the TOS-1A is particularly effective as the overpressure can kill or disable enemy troops inside buildings or bunkers as well as set off landmines and disable other types of explosive traps. Algeria some 52 TOS-1As and stationed the first ones to arrive on the Libyan border. It is unclear why Algeria purchased TOS-1A vehicles. Azerbaijan also ordered 36 of them and used them against Armenian forces in open areas with some success. Armenia has also purchased some TOS-1A vehicles of its own but it is unknown if there has yet been any TOS-1A on TOS-1A action yet.