During Denmark’s largest defense industry trade show, DALO Industry Days in Ballerup, held on August 20–21 of this year, Finnish companies Sisu Auto and Patria Oyj presented the TREMOS self-propelled mortar on the GTP 4×4 chassis.
Photo: Sisu Auto via X
While Patria Oyj was present at booth no. 309, the mortar in question was displayed at booth no. 304. It is the result of cooperation between the two companies, which had previously jointly developed the new 155 mm wheeled self-propelled howitzer ARVE (ARtillery on VEhicle).
The modular TREMOS (Traditional REborn MOrtar System) mortar system can be fitted with either an 81 mm or a 120 mm barrel; the latter, in a truck-mounted version, was ordered by Finland in October of last year and will enter service under the designation 120 KRH M3 (Modular Mobile Mortar).
The mortar module weighs 2,800 kg and is operated by a crew of three to four soldiers. The theoretical rate of fire is 12–15 rounds per minute, with the first three rounds fired within 15 seconds. The effective range depends on the ammunition used but is expected to exceed 7 km. The traverse range is 185°, with elevation angles from 40° to 80°. The system comes with an ammunition storage unit, a loading mechanism, and an inertial navigation system (INS) for aiming, and it can also be integrated into a battle management system (BMS).
Sisu Auto also showcased in Denmark a prototype of the GTT tracked articulated all-terrain vehicle (ATV), developed in cooperation with Singapore’s ST Engineering, which debuted in February of this year.
SISU GTP and @group_patria TREMOS. Mobility, Protection and Power together!#SISU #GTP #TREMOS pic.twitter.com/byKTeBeDAD
— Oy Sisu Auto Ab (@SisuAuto) August 20, 2025
Meet Sisu Auto at DALO Industry Days 2025, stand 304. We shall bring two SISU vehicles to the event, tracked #GTT and wheeled #GTP, both equipped with platform for 10’ mission modules and cargo. Shall we see in 🇩🇰? #daloindustrydays pic.twitter.com/9SU9R1c9eo
— Oy Sisu Auto Ab (@SisuAuto) August 6, 2025
As for the base chassis, modular GTP 4×4 vehicles have so far been ordered in a quantity of 260 units by Finland and Sweden (Latvia withdrew from the purchase). The combat weight is 16,500 kg, with a payload capacity of 5,000 kg. The vehicle measures 6,000 mm in length, 2,500 mm in width, and 2,550 mm in height. The wheelbase is 3,800 mm, and the ground clearance is 400 mm. The crew consists of 2 soldiers, with a maximum of 8 dismounts. The vehicle can negotiate obstacles with approach and departure angles of up to 45 degrees and side slopes of up to 37 degrees. It can ford to a depth of 1,200 mm and climb terrain with a gradient of 60%. Both ballistic and mine protection are said to meet STANAG 4569 standards (though no level was specified).
It is worth noting that in mid-November 2019, Sisu Auto unveiled this second variant, equipped with a new 6-cylinder, 4-stroke Mercedes-Benz OM926 diesel engine producing 243 kW (330 hp), along with an Allison 3500 automatic transmission and a ZF VG750 transfer case, which provides an operational range of over 700 km. The power-to-weight ratio is 22 hp/ton.
The original version of the GTP 4×4 was first presented at the Auto 2018 international exhibition in Riga. According to earlier announcements, additional variants are planned, including a recovery and rescue vehicle with a crane, an armored ambulance, and a reconnaissance vehicle.
Meanwhile, on July 24, a vehicle was unveiled equipped with a Trackfire ARES remotely controlled weapon station, developed in cooperation with Swedish company Saab Defence and Security.
New powerful duo – the new Trackfire ARES Remote Weapon system mounted on the 4×4 Sisu GTP. #trackfire #CUAS pic.twitter.com/dSQ4cgeW4A
— Saab (@Saab) July 24, 2025