152 mm howitzer-gun M1937 (ML-20)

The ML-20 saw action in World War II, mainly as a corps / army level artillery piece of the Soviet Army. Captured guns were employed by Wehrmacht and the Finnish Army. Post World War II, the ML-20 saw combat in numerous conflicts during the mid to late twentieth century.

• Name — 152 mm howitzer-gun M1937 (ML-20) • Type — Heavy gun-howitzer • Origin — Soviet Union • Is Ranged — yes • Is Artillery — yes • Used By — See users • Wars — * Winter War • World War II • Six-Day War • Yom Kippur War • Designer — Design bureau of No. 172 Plant, headed by F. F. Petrov • Production Date — 1937–1947 • Number — 6,884 • Weight — * combat: • travel: • Length — 8.18 m (with limber; barrel pulled back) • Part Length — bore: 4.24 m L/27.9 overall: 4.412 m L/29 (without muzzle brake) • Width — 2.35 m • Height — 2.27 m • Cartridge — 152×547mmR • Caliber — 152.4 mm (6 in) • Rate — 3–4 rounds per minute • Velocity — 655 m/s • Max Range — 17.23 km (10.7 mi) • Breech — interrupted screw • Recoil — hydro-pneumatic • Carriage — split trail • Elevation — -2° / 65° • Traverse — 58°

Among other artillery pieces the Red Army (RKKA) inherited from the Imperial Russian Army a 152-mm siege gun M1910, developed by Schneider. The gun was modernized twice in 1930s, resulting in the 152-mm gun M1910/30 and the 152-mm gun M1910/34. However, its mobility, maximum elevation and speed of traverse still needed improvement. In 1935–36 the No. 172 Plant in Motovilikha tried to continue the modernization works, but the Main Artillery Directorate (GAU) insisted on more significant upgrade. Consequently, the design bureau of the plant developed two guns ML-15 and ML-20. While the former project was initiated by GAU, the latter started as private development; the team working on it was led by F. F. Petrov. Both guns used barrel and recoil system of the M1910/34. The ML-20 also inherited the wheels, suspension and trails from the older gun. The ML-15 reached ground tests in April 1936, was returned for revision and was tested again in March 1937, this time successfully. The ML-20 went through ground tests in December 1936 and through army tests next year. After some defects (mostly in carriage) were eliminated, the ML-20 was recommended for production and on 22 September 1937 it was adopted as 152-mm howitzer-gun model 1937. It is not clear why the ML-20 was preferred. The ML-15 was lighter (about 500 kg less in combat position, 600 kg in traveling position) and more mobile (maximum transportation speed 45 km/h). On the negative side, the ML-15 had a more complicated carriage (however, the final version of the ML-20 carriage incorporated some features of the ML-15). Some sources claim that the choice was made because of the economic factor—the ML-20 was more similar to the M1910/34, thus requiring fewer adjustments for production.

The gun was in production from 1937 to 1946. 6,884 guns were manufactured and about 4,000 ML-20S barrels were used in the SU-152 and ISU-152 self-propelled guns. The ML-20 was eventually replaced by the D-20 152 mm gun with identical ballistics, which entered production in 1956. Production of МL-20s • Year — 1937 — 1938 — 1939 — 1940 — 1941 — 1942 — 1943 — 1944 — 1945 — 1946 — Total • Produced, pcs. — 148 — 500 — 567 — 901 — 1,342 — 1,809 — 1,002 — 275 — 325 — 15 — 6,884 Smaller production rates toward the end of the war were caused by two reasons. First, most of the barrels produced in these years were ML-20S. Second, after the Soviets started to field heavy tanks such as the JS series that used the A-19 122mm gun, the plant was ordered to increase the production of the A-19 instead of the ML-20.

• Illustration — ML-20 in Poznań Citadel, Poland. • Illustration — ML-20 in Hämeenlinna Artillery Museum, Finland. • Illustration — ML-20 in Hämeenlinna Artillery Museum, Finland. • Illustration — ML-20 in Batey ha-Osef Museum, Israel.

The ML-20 was originally intended for corps artillery. Together with the 122-mm gun A-19 it formed a so-called "corps duplex". In 1940–41 there were three types of corps artillery regiments: • With two battalions of ML-20 and one of either A-19 or 107-mm guns (a total of 24 ML-20s). • With two battalions of ML-20 and two of either A-19 or 107-mm guns (a total of 24 ML-20s). • With three battalions of ML-20 (a total of 36 ML-20s). Soon after the outbreak of Operation Barbarossa, the corps artillery was eliminated (as rifle corps themselves were eliminated). It was restored later in the war. The new corps artillery regiments were supposed to be armed with 122-mm guns or 152-mm howitzers, but some memoirs mention that the ML-20 was also used. From 1943 the gun was employed by artillery regiments of armies. Such regiments had 18 ML-20s. Guard armies from early 1945 had artillery brigades with 36 ML-20s. The ML-20 also used by artillery regiments (24 pieces) and brigades (36 pieces) of the Reserve of the Main Command. It was primarily used for indirect fire against enemy personnel, fortifications and key objects in the near rear. Heavy fragments of the OF-540 HE-Fragmentation shell were capable of piercing armour up to 20–30 mm thick, making a barrage dangerous to thinly armored vehicles and to some extent to heavier armoured ones as the fragments could damage chassis, sights or other elements; sometimes a close explosion caused damage inside a vehicle even though the armour remained intact. Direct hit of a shell often resulted in tearing away a turret of a medium tank or jamming it in case of a heavy tank. The first combat use of the ML-20 was in the Battle of Khalkhin Gol, in limited numbers. It also saw combat in the Winter War against the Mannerheim Line fortifications. The gun continued to be used throughout the World War II. Excellent characteristics of the gun, including reliability and ease of maintenance, allowed it to remain in service with the Soviet Army for a long time after the war.

In the early stage of the German invasion of the Soviet Union hundreds of ML-20 were captured by the Wehrmacht. The gun was adopted by Germans as 15.2 cm KH.433/1(r). From February 1943 Germans manufactured ammunition for the gun. The Finnish Army captured 37 guns of the type in 1941–44 and received additional 27 from Germany. These guns were adopted as 152 H 37. A number of barrels were mated with carriages of A-19 to create 152 H 37-31. While the gun was generally liked, the Finnish Army didn't possess enough prime movers suitable for towing such a massive piece. As a result, some of the guns were assigned to coastal artillery. Two pieces were captured back by the Red Army. A number of these guns were |modernized in 1988 and were in reserve until 2007 under the designation 152 H 88-37. After the war the ML-20 was widely exported to Warsaw Pact allies and to many states in Asia and Africa (in some of those states the gun still remains in service). It was adopted by Egypt and Syria and saw action in Arab–Israeli conflict. In 2002 a TV documentary featured ML-20 employed by the Afghan Northern Alliance forces against the Taliban fighters; it seems likely that the guns were initially supplied to the Najibullah's regime. In October 2025, during the Russo-Ukrainian war, Ukraine's 55th Artillery Brigade uploaded a video on their official social media accounts a video showing what appears to be a ML-20 being towed by a Russian truck in Donetsk, being followed by its destruction due to Counter-battery fire.

The barrel was manufactured in two variants − monobloc or built-up. Some sources indicate that a third type – with loose liner – also existed. Except the basic variant, the only variant to reach mass production was the ML-20S, developed for use in self-propelled guns, with differently placed controls for easier operation in small enclosed compartments. • ML-20 with bag loading – In 1937 the Main Artillery Department decided, for economic reasons, to modify medium caliber guns to use bag loading instead of cased loading. An experimental ML-20 piece was built in 1939; the trials were unsuccessful. • ML-20SM – Modified ML-20S with identical ballistics. muzzle brake was removed. The gun was mounted in the experimental ISU-152 model 1945, of which only one unit was built. • Illustration — Polish 152 mm howitzer-gun wz. 37/85 Lubuskie Military Museum • BL-20 – ML-20 with cast breech and wedge breechblock. Was developed by OKB-172 (sharashka of the NKVD) in 1946. • ML-20 with M-46-type carriage – ML-20 with a modified carriage, resembling in construction a carriage of the M-46 130 mm gun. In 1950 an experimental piece was built and tested. • 152 H 88-37 – A Finnish modernization program • 152 mm haubico-armata wz. 37/85 – A Polish modernization, tires from KrAZ-255B truck, new compressed air cylinder and automotive lighting increased the road speed of the towed gun from 20 to 50 km/h and allowed the gun to be towed on public roads.

• SU-152 – utilizing KV-1S heavy tank chassis, in production from February to December 1943, 670 units built. • ISU-152 – utilizing IS-2 mod 1943 and 1944 heavy tank chassis, in production from November 1943 to 1946, 3,242 units built. • Object 704 (ISU-152 model 1945) – a single prototype utilizing parts from IS-3 heavy tank chassis.

The ML-20 was one of the most successful Soviet artillery pieces of World War II. Its characteristics positioned it between classical short-range howitzers and special long-range guns. Compared to the former, the ML-20 has better range (e.g. the German 15 cm sFH 18 had range of 13.3 km), which often allowed it to shell positions of enemy artillery while remaining immune to enemy fire. Its advantage over the latter was in weight and cost, and therefore in mobility and production rate. For example, the German 15 cm K 39 with range of 24.7 km weighed 12.2 tons had only 61 pieces built. The excellent 17 cm K 18 (23.4 t, 29.6 km) had 338 pieces manufactured. The lighter 10.5 cm sK 18 (5.6 t, 19.1 km) was more common (2,135 pieces) but its 15 kg shell was much less powerful than a 44 kg shell of ML-20. German attempts to produce an analogue to the ML-20 were unsuccessful. The 15 cm sFH 40 was never produced due to construction defects; the 15 cm sFH 42 had insufficient range and only 46 pieces were built. In 1943 and 1944 Wehrmacht announced requirements for a 15 cm howitzer with a range of 18 km, but none reached production. Of other guns with more or less similar characteristics, there were French 155 mm guns model 1917 and 1918 with longer range, but some 3.5 tons heavier (as was the US 155 mm Long Tom). The Czechoslovak howitzer K4 (used by Germans as 15 cm sFH 37(t)) was about 2 tons lighter, but with range more than 2 km shorter and only 178 pieces were built. The Italian Cannone da 149/40 modello 35 had a range of 23.7 km but had a weight of 11 tons and less than 100 pieces were built. The British BL 5.5 inch (140 mm) Medium Gun probably had the closest characteristics; weight slightly over six tons and range of 18100 yd with an 82 lb shell. The main shortcomings of the ML-20 were its weight and limited mobility. As the experience of the ML-15 project suggests, the gun could be made somewhat lighter and more suitable for high-speed transportation. The use of a muzzle brake can be seen as a minor flaw: while softening the recoil and thus allowing the use of a lighter carriage, a muzzle brake has the disadvantage of redirecting some of the gases that escape the barrel toward the ground, where they can raise dust, potentially revealing the gun position. But when the ML-20 was developed, muzzle brakes were already a common design element in artillery pieces of that class.

• Available ammunition • Type — Model — Weight — Filler weight — Muzzle velocity — Range • Armor-piercing shells • APHE — BR-540 — 48.80 kg — 0.66 kg — 600 m/s — 4000 m • APBC (from late 1944) — BR-540B — 46.5 kg — 0.48 kg — 600 m/s — 4000 m • Naval semi-AP — Model 1915/28 (PB-35) — 51.07 kg — 3.2 kg — 573 m/s • HEAT — BP-540 — 27.44 kg — 680 m/s — 3000 m • Anti-concrete shells • Anti-concrete howitzer shell — G-530 / G-530Sh — 40.0 kg — 5.1 kg • Anti-concrete gun shell — G-545 — 56.0 kg — 4.2 kg • High-explosive and fragmentation (gun) shells • HE-Fragmentation, steel — OF-540 / OF-540Sh — 43.6 kg — 5.90–6.25 kg — 655 m/s — 17,230 m • HE, old — F-542 — 38.1 kg — 5.86 kg • HE, old — F-542G — 38.52 kg — 5.83 kg • HE, old — F-542Sh — 40.6 kg — 6.06 kg • HE, old — F-542ShG — 41.0 kg — 5.93 kg • HE, old — F-542ShU — 40.86 kg — 5.96 kg • HE, old — F-542U — 38.36 kg — 5.77 kg • High-explosive and fragmentation (howitzer) shells • HE-Fragmentation, steel — OF-530 — 40.0 kg — 5.47–6.86 kg • HE-Fragmentation, steely iron — OF-530A — 40.0 kg — 5.66 kg • HE, old — F-533 — 40.41 kg — 8.0 kg • HE, old — F-533K — 40.68 kg — 7.3 kg • HE, old — F-533N — 41.0 kg — 7.3 kg • HE, old — F-533U — 40.8 kg — 8.8 kg • HE, steely iron, old, French — F-534F — 41.1 kg — 3.9 kg • HE, for 152-mm mortar model 1931 — F-521 — 41.7 kg — 7.7 kg • HE, British, for Vickers 152-mm howitzer — F-531 — 44.91 kg — 5.7 kg • Shrapnel shells • Shrapnel with 45 sec. tube — Sh-501 — 41.16–41.83 kg — 0.5 kg (680–690 bullets) • Shrapnel with Т-6 tube — Sh-501T — 41.16 kg — 0.5 kg (680–690 bullets) • Illumination shells • Illumination, 40 sec. — S 1 — 40.2 kg • Chemical shells • Fragmentation-chemical gun shell — OH-540 • Chemical howitzer shell — HS-530 — 38.8 kg • Chemical howitzer shell — HN-530 — 39.1 kg • Chemical (post-war) — ZHZ

• English abbreviations: • AC – anti-concrete • AC-F – anti-concrete fragmentation • APHE – armour-piercing high-explosive • APHE-BC – armour-piercing high-explosive ballistic-capped • cnn. – cannon shell • (CS) – cast steel shell • how. – howitzer shell • HE – high-explosive • HE-C – high-explosive chemical • HEF – high-explosive fragmentation • HEAT – high-explosive anti-tank • max. – maximum • min. – minimum • nav. – naval shell • (OP) – ogive point shell (остроголовая граната) • (RP) – round point shell (тупоголовая граната) • SAPHE – semi armour-piercing high-explosive • (ST) – steel shell • Russian abbreviations: • БР – prefix: бронебойные (armour-piercing) • БП – prefix: бронебойный противотанковый (armour-piercing anti-tank) • Г – prefix: гаубичный (howitzer) or граната (shell) • Ж suffix: – железокерамическим пояском (cermet driving band) • ЗХЗ – prefix: зона химического заражения (zone of chemical contamination) • обр. – о́браз (mod) • ОФ – prefix: осколочно фугасный (fragmentation high-explosive) • ОХ – prefix: осколочно химический (fragmentation chemical) • С – prefix: световой (luminous) • Ф – prefix: фугасный (high-explosive) – suffix: французский (French) • ХН – prefix: химический нестойкими (chemical unstable) • ХС – prefix: химический стойкими (chemical persistent) • Ш – prefix: шрапнель (shrapnel shell) – suffix: шрапнель (shrapnel)

Armour penetration table • APHE shell BR-540 • Distance, m — Meet angle 60°, mm — Meet angle 90°, mm • 500 — 105 — 125 • 1000 — 95 — 115 • 1500 — 85 — 105 • 2000 — 75 — 90 • APBC shell BR-540B • Distance, m — Meet angle 60°, mm — Meet angle 90°, mm • 500 — 105 — 130 • 1000 — 100 — 120 • 1500 — 95 — 115 • 2000 — 85 — 105 • Naval semi-AP model 1915/28 • Distance, m — Meet angle 60°, mm — Meet angle 90°, mm • 100 — 110 — 136 • 500 — 104 — 128 • 1000 — 97 — 119 • 1500 — 91 — 111 • 2000 — 85 — 105 • These data was obtained by Soviet methodology for armour penetration measurement (penetration probability of 75%).Values are not directly comparable with other methods for estimating penetration.

World War II • Soviet Union • Nazi Germany • Finland • – small number of captured German pieces used for evaluation • – small number of captured German pieces used for evaluation Post-war • Soviet Union • Afghanistan • Albania • Algeria • Bulgaria – ≈165 • China • Cuba • Czechoslovakia • Egypt • Finland • Georgia • East Germany • Iraq • North Korea • Libya – ≈25 • Mongolia • Namibia • Poland – 135 • Romania – 154 • Russia – ≈100 • Somalia • Syria • Ukraine • Vietnam Present Day • Algeria – 20 • Cuba • Mongolia • Russia – ≈100 in storage • Syria

• Illustration — ML-20 guns in Saint Petersburg. ML-20s are on display in a number of military museums. Among other places, the gun can be seen: • In the Central Armed Forces Museum and at the Poklonnaya Hill, Moscow, Russia. • In the Museum of Artillery and Engineering Forces, Saint Petersburg, Russia. • In The Artillery Museum of Finland, Hämeenlinna, Finland. • In the IDF History Museum (Batey ha-Osef), Tel Aviv, Israel. • In Poznań Citadel, Poland. • In the Lubuskie Military Museum, Drzonów, Poland. • In the US Army Ordnance Museum, Aberdeen, Maryland, United States. • At the Soviet War Memorial, Tiergarten, Berlin, Germany. • In the National Military Museum, Romania, Bucharest. • In the Military Museum, Dej, Romania. • In the Arsenal Park resort, Orăștie, Romania. • In the Pivka Park of Military History, Slovenia