Finland improves indirect fire capabilities with new GTP TREMOS 120mm self-propelled mortar.

At the DALO Industry Days held in Ballerup, Denmark, on August 20–21, 2025, the Finnish company Sisu presented Finland’s new self-propelled mortar, combining the Sisu GTP 4x4 multi-role armored vehicle with Patria’s TREMOS modular mortar system. Patria’s main stand was located at 309, while the TREMOS mounted on the Sisu platform was displayed at stand 304. The two companies previously collaborated on Finland's first wheeled self-propelled howitzer, the ARVE, which combines a 155K98 field gun and a Sisu E13TP 8×8 truck.
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The strengths of the new GTP TREMOS self-propelled mortar are that it can be fitted with either a 120 mm or an 81 mm smoothbore mortar tube, while allowing for quick withdrawal to reduce vulnerability, thanks to a top speed of more than 100 km/h. (Picture source: Sisu Auto)

Alongside this system, Patria also highlighted its 6x6 vehicle fitted with a SIMA ringmount ordered by Denmark within the multinational Common Armoured Vehicle System (CAVS) program, as well as its sustainment solutions under Patria OPTIME. These included the ILIAS digital defense platform, developed by Belgian-based ILIAS Solutions, which Patria acquired in January 2025 to provide mission-driven logistics and real-time fleet visibility. This broad showcase emphasized Finland’s integration of mobile artillery systems with domestic armored carriers while also promoting long-term sustainment and cooperation with European partners.

The Patria TREMOS mortar system, an acronym for Traditional REborn MOrtar System, is a modular solution designed to increase the mobility and survivability of traditional mortars. It can be fitted with either a 120 mm or an 81 mm smoothbore mortar tube, using existing barrels, breeches, ammunition, and ballistic tables, which reduces the need for retraining and ensures compatibility with current stocks. Its hydro-pneumatic recoil system, originally derived from Patria’s NEMO turreted mortar, allows the weapon to be fired without deploying a ground baseplate, which enables fast relocation after firing. Operationally, the system can fire within 60 seconds of reaching a position and leave immediately after the last round. The rate of fire is quoted at 12 to 15 rounds per minute, with the first three rounds launched in just 15 seconds. Depending on the ammunition, the range is over 7 kilometers. A typical crew consists of three to four members, including a commander, gunner, and one or two loaders, all seated in dedicated operating positions that reduce emplacement time.

A defining feature of TREMOS is its modularity. The system is mounted using ISO-standard twist-locks, which makes it transferable between different vehicles, from military trucks to commercial flatbeds, within minutes in field conditions using equipment such as a forklift or hook lift. After its demonstration in Finland, Patria transported the TREMOS system to Sweden to show its installation and firing capability from a standard commercial vehicle with a hook lift, highlighting its ability to adapt to a wide range of carriers. An integration module weighing approximately 2,800 kg secures the mortar to the vehicle, while a complete configuration with options weighs around 3,000 kg. The design includes modular ammunition storage and preparation compartments, which increase safety in handling charges and fuses. Options include inertial navigation, battle management system connectivity, muzzle velocity radar, an optical backup sight, and a double-load warning device. The combination of rapid setup, modular integration, and optional systems gives operators the ability to move the mortar from one platform to another, preserving operational capacity even if a carrier vehicle is lost.

Patria launched the TREMOS at the Future Mortar Systems conference in London on October 29, 2024. The Finnish Defence Forces subsequently announced plans to procure the system under the designation 120 KRH M3. A pre-series of the system is expected to be delivered to the Finnish Army in 2025. According to Patria, the prototype was developed in less than a year in cooperation with the Finnish Defence Forces and its Logistics Command, building on lessons learned from previous Patria mortar programs such as AMOS and NEMO. The system is intended to address the vulnerabilities of traditional mortars, which in modern conflicts are increasingly exposed to counter-battery fire and aerial detection by unmanned systems. By integrating existing mortar components with vehicle-mounted modular structures, Finland seeks to improve the mobility and responsiveness of its indirect fire units without requiring a full replacement of its mortar inventory.

The Sisu GTP, used as the host vehicle at DALO 2025, is a Finnish mine-resistant ambush protected 4x4 armored vehicle first produced in 2018 by Oy Sisu Auto Ab. It is based on a Mercedes-Benz Unimog chassis and incorporates independent suspension with Texelis T700 axles. The vehicle weighs 16.5 tonnes, is 6 meters long, 2.5 meters wide, and 2.55 meters high, with a payload capacity of 5 tonnes. It is powered by a Mercedes-Benz OM926 six-cylinder diesel engine producing 308 horsepower, giving it a top road speed of more than 100 km/h, an operational range of over 700 km, and an amphibious speed of 12 km/h in water. Ground clearance is 400 mm, and the vehicle is designed to ford water to depths of up to 850 mm. It has approach and departure angles of 45°, a stability tilt of 37°, and the ability to climb gradients of up to 60 percent. The standard armor meets STANAG 4569 Level 1, with options for add-on kits including EFP and RPG protection, as well as CBRN overpressure systems. Its modular backbone supports multiple mission modules, including troop transport for 10 soldiers, reconnaissance, command and control, medical evacuation, logistics, and air-defense variants.

Procurement of the GTP is underway in both Finland and Sweden as part of their joint framework agreement known as FISE. Finland initially ordered six GTPs for trials in 2020, followed by 25 production vehicles in 2022, and a further 13 in 2023 for approximately €9.7 million, excluding VAT. These acquisitions were justified on grounds of improving troop mobility, strengthening national security of supply, and supporting domestic industry. Sweden, which designates the vehicle as TGB24, received its first deliveries in 2024 through its materiel agency FMV, including troop transport and double-cab cargo versions. In total, over 260 vehicles are to be jointly procured by both countries in multiple configurations, including CBRN reconnaissance, air-defense, ambulance, and logistics variants. Sweden also awarded Saab a contract worth about SEK 700 million to integrate the Giraffe 1X radar onto the GTP platform as part of its short-range air-defense network, with deliveries scheduled between 2024 and 2027. Training and verification of the vehicles began in Sweden in late 2024, with operational readiness targeted shortly thereafter.

At DALOS 2025, the joint appearance of the Sisu GTP and Patria TREMOS illustrated Finland’s broader strategy of combining domestic armored platforms with modular artillery systems that enhance flexibility and survivability in fast-changing operational environments. Patria also used the event to showcase its Patria 6x6 within the multinational CAVS program, where nearly 1,000 vehicles have been ordered and more than 200 delivered, and to highlight its OPTIME sustainment concept supported by the ILIAS software platform. The TREMOS and GTP integration demonstrated not only Finland’s modernization of its indirect fire capabilities but also its integration into a Nordic and European industrial context that emphasizes interoperability, modularity, and rapid adaptation to the demands of current and future conflicts.