Russia admits to a missing link in its air defense systems. This was made clear at the end of 2017 when the Russian controlled Hmeimim (or “Khmeimim”) airbase in northwest Syria came under regular attack by 82mm mortars. Russian weapons experts quickly concluded that the weapon used was probably a Russian 2B9 Vasilek (Cornflower) automatic 82mm gun-mortar. The evidence was the shell fragments from 3.24 (7.2 pound) 82mm shells and the fact that the shells were fired quickly. The 2B9 can use a four round clip that fires four 82mm shells in about two seconds. The Russian analysts realized that the only weapon that could have done that was the 2B9 but because Russia had never sold 2B9s to Syria the Russians accused Turkey of allowing Turkish smugglers to get such a large weapon across the border and into rebel hands. Turkish intelligence quickly eliminated that by pointing videos posted on YouTube in 2014 showing Syrian Islamic terrorist rebels using what was clearly a 2B9. This is not a small weapon and weighs 632 kg (1,400 pounds), is mounted on two wheels and looks like towed artillery, which it is, except it uses the same ammo as the 82mm mortar and can be fired using those four round clips or by dropping the 82mm mortar shell down the barrel as most mortars operate. The 2B9 has been manufactured in Russia since 1970 and by the 1980s China was manufacturing a clone called the W99. The Turks pointed out that Syrian rebels had, since 2014, boasted of capturing 2B9s from the Syrian army. How the Syrian army got them is an issue best not pursued by the Russians because 2B9s were in use by the Syrian army before 2011 and it is believed they were obtained from arms dealers or were Chinese W99s (you have to examine a W99 closely to be sure it is not a 2B9). After all that came to light the Russians no longer blamed the Turks or wanted to discuss the 2B9 but did lament in the media that they do not have a weapon to stop 82mm shells while the Israelis, Americans and even the Germans do.
The American “anti-mortar” system has been in use since 2006 and is a modified naval weapon (Phalanx) called C-RAM. This weapon has a range of about 2,000 meters and can knock down 70-80 percent of the rockets and mortar shells fired within range of its cannon. C-RAM uses high explosive 20mm shells that detonate near the target, spraying it with fragments. By the time these fragments reach the ground they are generally too small to injure anyone. At least that's been the experience in Iraq and Afghanistan. The original Phalanx used 20mm depleted uranium shells, to slice through incoming missiles. Phalanx fires shells at the rate of 75 per second. Another advantage of C-RAM is that it makes a distinctive noise when firing, warning those nearby that a mortar or rocket attack is underway, giving people an opportunity to duck inside if they are out and about. Germany later developed their own 35mm take on C-RAM while China developed a 30mm version that never caught on, even within the Chinese military. C-RAM and the German Mantis remain in service. Both of these offer short range defense, which is ok for protecting a base, or even an airfield. Israel developed a more ambitious solution.
The Israeli solution is Iron Dome, which has been in service since 2009 and has proven itself in combat. By 2011 Israel had bought seven batteries of it, each battery has radar, control equipment, and 3-4 missile launchers (each with 20 missiles) and cost about $37-50 million. Iron Dome uses two radars to quickly calculate the trajectory of the incoming rocket or mortar shell and does nothing if the trajectory indicates the rocket or shell is going to land in an uninhabited area. But if the computers predict something coming down in an inhabited area, a $50,000 Tamir guided missile is fired to intercept the rocket. This makes the system cost-effective. So far Iron Dome has shot down 85 percent of the rockets it calculated were headed for populated areas. The Tamir missiles used by Iron Dome weigh 90 kg and have a range of 70 kilometers against rockets, mortar shells, and artillery shells up to 155mm. Iron Dome can also shoot down aircraft and helicopters (up to 10 kilometers/32,000 feet). Apparently one reason for the current military alliance between Israel and Saudi Arabia was the Saudi (and other Gulf Arab states) desire to buy Iron Dome systems, which are seen as a more efficient solution for rocket/mortar attacks than C-RAM.
Meanwhile Russian intelligence believes Syria rebels have mounted a 2B9 on the back of a truck or large van and rigged to quickly roll out the back, fire one or two clips of 82mm shells, they be hauled back in the truck and driven away, or back into a building or cave so that Russian aircraft or UAVs cannot track it down. But the Russian activity has apparently scared the mortar users away for the moment. The mortar attacks were an issue because they caused several million dollars damage to Russian warplanes at the base and killed several Russians. The Russians prefer to develop an offensive solution for this problem, which can be as effective, in Russian eyes, as C-Ram or Iron Dome.