The mobile Multiple Launch Rocket System (MLRS) - or rocket projector - has remained a stable of modern military forces since the days of World War 2 (1939-1945). The Soviets used such systems to great effect against the Germans and all major sides of the conflict fielded some sort of MLRS unit on those battlefields. Into the Cold War decades (1947-1991), the MLRS saw continued use with more world powers than before, resulting in a plethora of developments to come down the pipeline. One such system to emerge from the former Yugoslavia during the 1970s became the M-77 "Oganj". Its NATO designation was "YMRL-32".
The M-77 was nothing more than a mating of a 32 x 128mm launch rack (sat atop a trainable mounting) and the Yugoslav FAP 2026 BDS/A 6x6 wheeled military truck. The resulting system proved highly effective for the rocket-projecting role and was, by and large, very similar in form and function to the many Soviet-inspired truck-based rocket projectors appearing during the Cold War period.
Design work on the M-77 began as early as 1968 but it was not until 1975 that the system was publically unveiled. Formal service began in 1977 (hence its designation) and hundreds of examples then followed out of production facilities. The 50,000 lb vehicle was crewed by five personnel and sported a length of 27.6 feet, a width of 8 feet and a height of 10 feet. A FAP 8-cylinder diesel-fueled engine powered the vehicle portion of the M-77 and could reach 50 miles per hour on paved roads. The 128mm rockets were 8.5 feet in length and completed with 44lb warhead for maximum High-Explosive (HE) effect. The projectiles held a lethal range out to 12 miles from the launcher. The crew was offered modest local defense through a 12.7mm Heavy Machine Gun (HMG), and any personal weapons carried by the crew, while the cabin was only lightly armored and protected the operating crew minimally.
The system's arrangement was conventional as Multiple Launched Rocket Systems (MLRSs) went - the truck crew cab and engine were fitted forwards with a flatbed sat over rear to allow for the installation of the rocket launcher unit. The truck's original 6x6 wheeled suspension system gave good cross-country performance as well as excellent ground clearance over uneven terrain and when wading through water sources.
The M-77 saw considerable use in the Balkan Wars (1991-2001) that followed and was one of the few indigenous Yugoslavian artillery pieces to serve in the conflict. The vehicle launcher provided exceptional service in saturating known enemy positions though the eventual dissolution of Yugoslavia meant that the existing units were dispersed in uneven amounts between the various warring parties - Bosnia and Herzegovina, Croatia and Serbia with Serbia maintaining the lion's share of the stock. These remained in service with their respective forces after the war ended.
Today, the Serbian Army is known to manage a collection of some 130 total M-77 systems and Bosnia and Herzegovina holds in inventory about 36 M-77 units. Croatia originally phased out its M-77 units but has since (2015) reinstated the fleet of about a dozen vehicles. A later modification to the base M-77 design produced the "Oganj 2000 ER" mark which was able to fire the Soviet BM-21 "Grad" system's 122mm rocket from a 50-count launcher. Similarly, the Croatian Army modified their M-77 stock to support a 122mm rocket by way of the M-91 "Vulkan" mark. Still another related M-77 development - this to come out of Serbia - became the M-94 "Oganj C" which was able to fire two rocket types (HE and cluster) from the same launcher unit. This form first appeared in 1994 (hence its designation).