Recent events in Ukraine have demonstrated that anti-tank guns can still be useful on today's battlefields. After the end of the Cold War in 1991 towed anti-tank guns were considered to be an obsolete weapon. This was a long process, staring in the 1950s when lighter, more mobile recoilless rifles appeared then by more and more affordable and effective, longer ranged and far easier to transport guided anti-tank missiles (ATGMs).
Yet in the former Soviet satellite states of East Europe, these towed guns continued to be used and development of new models continued. Two of the post-World War II models were the 100mm T-12 and several variants) and the 125mm 2A45 Sprut-A. As more and better ATGMs became available more of the guns were put into storage, assigned to reserve units, or sold to countries that could not afford ATGMs.
Despite ATGMs advantages, the traditional anti-tank guns have few of their own. They are cheaper and simpler, doubly so their ammunition. A typical ATGM costs between $25,000 and $100,000 per missile, some of the more recent designs are even more expensive. In contrast most anti-tank gun shells to cost less than $1,000 each. Even the most modern and expensive of Western unguided anti-tank tank cannon shells, the M829E4, due to be fielded in 2016, will cost $10,100. The low cost of anti-tank gun shells makes it practical to train guns crews to a high standard than is the case with ATGM launcher operators. Guns and their ammunition also require less maintenance than ATGM launchers and their missiles, and what maintenance they require is cheaper and less technologically challenging.
These advantages led to more anti-tank guns being used over the last year in Ukraine by both sides. There the most commonly seen weapon was the MT-12 Rapira 100mm smoothbore gun. This is an improved version of T-12 gun, which first appeared in the 1950s. This gun has a shield to protect the crew from machinegun fire and shell fragments, and an improved carriage allowing the gun to be also towed by MT-LB series armored vehicles. Earlier versions could be only towed by trucks. The delicate ATGMs were often poorly stored and maintained, especially since the Cold War ended and were now often unreliable and in cases even dangerous for their users. Buying new missiles was often not an option because of the high cost. And even if new ATGM were obtained there was the temptation to skip training because of the expense. In contrast the anti-tank guns could be easily taken out of storage, checked over by a mechanic and be ready to go. Because of their simplicity and cheap ammunition new operators could be trained quickly.
One Ukrainian variant of the MT-12, called the MT-12R Ruta was particularly effective. The MT-12R had a RLPK-1 radar mounted on the gun, allowing the crew to spot and engage armored vehicles at long distance in low visibility conditions, even in conditions where thermal imaging sights did not work well.
While the MT-12 could fire the same ammo as the widely used (in East Europe) T-55 tanks, it had a somewhat longer barrel, giving it some additional accuracy and range. However, it does little to fix the gun's main shortcoming; the obsolete ammunition types available, combined with the relatively small caliber of the gun when compared to modern 120-125mm ones. As a result the 100mm guns are incapable of penetrating some (in the front) modern tank armor. To be effective against modern tanks the 100mm shells had to be fired at the sides or rear where the armor was thinner and usually not covered by additional protection (composite armor or the ERA heavy explosive reactive armor bricks.)
The more modern 125mm Sprut-A is based on the T-72 tanks cannon. This weapon can penetrate frontal armor on many modern tanks if the most modern shell designs are used. But since the Sprut-A entered service just before the Cold War ended, Ukraine could not afford to buy many of them. Meanwhile hundreds of the older MT-12s were put in storage in the1990s, just in case.
Despite its shortcomings the MT-12 was very useful in combat. That was because most armored vehicles encountered were not tanks and the 100mm shells could easily penetrate the lighter armor. The MT-12 was also useful against buildings and fortifications. The MT-12 could also fill in as artillery because its max range for explosive shells was 8.2 kilometers.
Most ATGMs are limited to firing at targets which the launcher operator can see, and even though some modern ones have missile variants for use against targets other than vehicles, only the wealthiest armies can afford to use the expensive guided missiles for that, while simple high explosive shells are cheap and easy to produce.
Just like the tank gun it's based upon, MT-12 can fire the 9M117 Bastion laser guided ATGM, which gives it improved range and armor penetration capability sufficient to threaten frontal armor of tanks most commonly used in the war (T-64 and T-72), as long as they are not equipped with ERA, however the missiles are in short supply in Ukraine, largely because they are expensive.
Because of the need for towing and setup afterwards, towed guns are not nearly as mobile as tanks and self- propelled guns, however they can be used for defense and ambushes, freeing some of the limited amount of available tanks for duties that make better use of their mobility and armor. --Adam Szczepanik