The Finnish defense corporation Oy Sisu Auto Ab has demonstrated its Sisu GTP 4×4 armored vehicle with Patria´s 120mm Tremos modular mortar system. Originally introduced in 2018, the Sisu GTP is a mine-resistant ambush protected (MRAP) vehicle built upon a heavy-duty Mercedes-Benz Unimog chassis combined with an independent suspension system utilizing Texelis T700 axles. With a gross vehicle weight of 16.5 tonnes and a generous payload capacity of 5 tonnes, the vehicle measures 6 meters long, 2.5 meters wide, and 2.55 meters high. Propulsion is provided by a Mercedes-Benz OM926 six-cylinder diesel engine generating 308 horsepower, which propels the platform to maximum road speeds exceeding 100 km/h, provides an operational range of over 700 km, and enables an amphibious swim speed of 12 km/h. Designed for demanding off-road environments, the Sisu GTP boasts a ground clearance of 400 mm, an unassisted fording depth of up to 850 mm, approach and departure angles of 45°, a side-slope stability tilt of 37°, and the ability to negotiate 60 percent gradients. This highly survivable modular backbone allows the platform to be rapidly reconfigured via interchangeable mission modules, supporting diverse roles including troop transport for up to 10 soldiers, reconnaissance, command and control, medical evacuation, logistics, and air defense.
Officially launched at the Future Mortar Systems conference in London on October 29, 2024, Traditional REborn MOrtar System (TREMOS) was developed as a working prototype in less than a year through a close collaboration between Patria, the Finnish Defence Forces, and its Logistics Command. During the DALO 2025 exhibition, the TREMOS system was showcased integrated onto the Sisu GTP 4×4 armored vehicle. Capitalizing on operational insights and engineering expertise derived from Patria’s previous advanced mortar programs—specifically the AMOS and NEMO systems—the TREMOS is engineered to mitigate the high vulnerabilities of traditional towed or static mortars in modern high-intensity conflicts, where assets are increasingly exposed to rapid counter-battery fire and aerial detection by unmanned aerial systems. Following its unveiling, the Finnish Defence Forces announced procurement plans for the system under the local military designation 120 KRH M3, with an initial pre-series delivery expected to reach the Finnish Army in 2025.
Functionally, the TREMOS can be configured with either a 120 mm or an 81 mm smoothbore mortar tube, utilizing preexisting barrels, breeches, ammunition inventories, and ballistic tables. This design philosophy dramatically reduces the burden of personnel retraining and ensures seamless logistical compatibility with existing military stocks. A core capability of the system is its hydro-pneumatic recoil mechanism, which inherits technology from Patria’s NEMO turreted mortar system. This mechanism allows the weapon to absorb firing forces directly through the vehicle chassis, completely eliminating the traditional requirement to deploy a ground-anchored baseplate before firing. Consequently, indirect fire units can achieve exceptional operational responsiveness, bringing the system into action within 60 seconds of arriving at a designated position and initiating a rapid displacement immediately after the final round is discharged. The system delivers a sustained rate of fire between 12 and 15 rounds per minute, with an intense surge capacity capable of launching the first three rounds in just 15 seconds, reaching a maximum operational range of over 7 kilometers depending on the specific ammunition utilized. The system is operated by a streamlined crew of three to four personnel, comprising a commander, a gunner, and one or two loaders, all of whom are positioned in dedicated operating seats designed to optimize workflow and reduce total emplacement timelines.
A defining architectural characteristic of the TREMOS is its high degree of modularity, leveraging standard ISO twist-locks to secure the weapon assembly to host platforms. This engineering choice permits the mortar system to be swapped between different vehicular assets—ranging from tactical military trucks to commercial flatbeds—within minutes under austere field conditions using standard logistics equipment such as forklifts or hook lifts. To demonstrate this flexibility, Patria transported the system to Sweden following initial trials in Finland, successfully validating its installation and live-fire capabilities from a standard commercial truck equipped with a hook lift mechanism. The core integration module weighs approximately 2,800 kg, which increases to around 3,000 kg when fully configured with optional subsystems. The layout features modular ammunition storage and secure preparation compartments to enhance safety during the handling of propellant charges and fuses. Operators can further customize the TREMOS with a suite of advanced electronic options, including an inertial navigation system, direct integration with automated battle management systems, a muzzle velocity radar, an optical backup sight, and a dedicated double-load warning device to prevent catastrophic tube failures.
