Finland signs for Patria’s TREMOS mortar system

By Sam Cranny-Evans, published on 12th November 2024. This post was amended on 12th November 2024 to include input from our readers. Thank you. 

The Finnish Army has signed a contract with Patria to purchase a pre-series of the company’s new TREMOS mobile mortar system for delivery in 2025, according to a 29th October press release from Patria. 

The Finnish Army, working with its Logistics Department and Patria, has developed the mortar under a project called 120 KRH M3 (Modular Mobile Mortar) in order to modernise its existing stock of 120 mm KRH towed heavy mortars by making them vehicle mounted and more mobile. “After the initial ideas were approved, it took only a year to produce the first prototype for proof-of-concept tests. The main objective was to significantly increase the mobility of an existing mortar equipment,” Lauri Pauniaho, Director, Weapon Systems at Patria said. TREMOS has already been through initial firing tests to demonstrate the concept. 

The deal was signed with Patria at a value of 4.7 million Euros and the first system will be delivered in 2025 ahead of initial conscript training in 2026, Colonel Ari Lehmuslehti, Inspector of Infantry from the Finnish Army’s headquarters, said in a press release from the Finnish Army announcing the procurement. The plan is to gather user experience from the pre-series procurement announced on the 29th October and use that to inform a future procurement decision. 

Finland is estimated to have 698 120 mm and 716 81 mm towed mortars and its mobilisation strength is around 285,000 according to the 2024 issue of The Military Balance from IISS. Not all of these mortars are in active use, the large stock is designed to equip the country’s reserve formations during a major conflict. So, the total quantity of TREMOS systems procured could reach into the hundreds if it successfully passes its pre-series evaluation. 

Tech profile: TREMOS

TREMOS is a modular system that is designed to be fitted to a vehicle and accept existing mortar tubes in either 81 mm or 120 mm as well as their qualified ammunition, meaning that existing ballistic tables can be used, speeding up the qualification process. It can be mounted on various vehicles from 4x4s to 8x8s, according to Patria. 

The design includes a hydropneumatic recoil buffer that helps to minimise the stress based on the vehicle chassis. It can be crewed by two or three personnel with one gunner and two loaders as required and fire within 60 seconds of the vehicle coming to a stop. As is common for mortars, the rate of fire is high – 12 – 15 rounds per minute, and a well-rehearsed crew can fire three rounds within 15 seconds of opening fire. Once the fire mission is complete, the vehicle can leave the area immediately to evade counter-battery fire. 

TREMOS is also designed to be integrated into existing battle management and fire control systems and can be equipped with an inertial navigation unit so that it can be coordinated with other effects and units on the battlefield. And, according to Patria, its modular design allows the system to be moved from one vehicle to another. 

Once installed, TREMOS allows the mortar to be traversed through ±185º and elevated from +40º to +80º. A typical integration module and mortar would have a total weight of 2,800 kg, which is indicative of the minimum vehicle size that would be required to carry it. 

Calibre comment

Mobility contributes to improved survivability of indirect fire systems like mortars. A towed mortar can take minutes to unhook from its vehicle and dig into place ready to fire. They are also very heavy, the Heavy Mortar 120 KRH used by the Finnish Army, for example, has a total weight of 500 kg. The drive gear alone weighs 215 kg and the tube is 100 kg. This means that these systems cannot be moved quickly, and the likelihood is that a crew would disperse away from the mortar rather than move it if they became aware of an enemy drone or received incoming fire. So, by mounting the mortar on a vehicle that requires little to no setup before firing, Finland can improve the survivability of its mortar crews by allowing them to move as soon as a fire mission is complete, which minimises the window for an opponent to detect and locate the source of fire and bring their own rounds down on the target. 

That said, there is evidence in Ukraine of Russian units deliberately bumping Ukrainian howitzers out of their hides by firing at them with artillery. They do this so that they can engage them with a Lancet loitering munition once the howitzer is on the road. The current school of thought on artillery survival tends to emphasise the need for rapid movement between positions and to relocate once guns have been unmasked. Russia’s tactics in Ukraine indicate that this may not always improve survivability. 

In addition to survivability, however, the Finnish Army emphasises mobility in its doctrine and expects its units to move quickly and to exploit their terrain to maximise lethality and effect against an invading Russian force. In that case, the development of TREMOS is a sound decision, as it will enable infantry brigades to take firepower with them and support their indirect fire needs with greater mobility.