During peace time there were The 7 pioneer regiments (1st-7th). At the beginning of the war they were divided: 8 battalions for the 7 corps and the Mountain Corps (51st-55th, 57th, 58th, 61st); 26 divisional battalions (1st-11th, 13th-15th, 18th-21st, 25th, 27th, 30th-32nd, 35th, 36th, 40th), 4 mountain pioneer battalions (1st-4th), one motorized pioneer battalion (for the 1st Armored Division) and two battalions (1st-2nd) for the Fortification Division. There also 8 road-building battalions and 22 different companies (deforestation, hydrology, design and others).
A divisional battalion was made up of 3 pioneer companies and a battalion train. Each company consisted of 3 pioneer platoons and one flame-thrower section. The platoon had 3 pioneer squads of 3 teams each. The battalion train was made up of a river crossing materials section, a mines and destruction materials section, a workshop section and a train section. It also had two assault deck teams.
A mountain pioneer battalion had 2 companies and a battalion train made up of a munitions and medical materials section, a mines and destruction section, a river crossing materials section, a workshop section and a motor air-compressor.
The pioneer battalion assigned to a corps had the following structure: 1st Motorized Pioneer Company, 2nd Mounted Pioneer Company and 3rd Road-building Company. The 1st and 2nd companies had an identical organization (in case of lack of vehicles, the 1st Company used horses): 3 pioneer platoons and a company train (3 sections of 3 teams each). The 3rd company had two pioneer platoons and a bridge platoon. The battalion train was equipped with wagons, motor air-compressors, tractors, trucks, road-builders, scrapers etc.
In the spring of 1941, the 2nd, 3rd, 4th and 7th road-building battalions were put at the disposal of the 6th Transport Section of the General Headquarters. A road-building battalion was made up of 6 companies: 3 road companies, one wooden bridge company, one quarry company and a motor air-compressor section.
The pioneers were equipped with Romania MAN model 1939 AT mines as well as anti-infantry mines. The explosives were transported in explosives carts model 1935, built by the Resita Works. They used the Brickford water-tight fuse, MAN model 1930 fuse (with mercuric fulminate), MAN model 1935 electric detonators etc.
The river bridges model 1893 and model 1912 were used to cross water courses. There were also MAN model 1939 assault decks. An assault deck team had 15 boats and 16 boxes, which could be assembled into a 60 m long deck, on which the infantry could cross with its individual equipment.
After the military operations started the pioneers received German made Berlin 40 mine detectors. After the operations in Bessarabia and Bucovina ended, the corps pioneer battalions were put at the disposal of the General Headquarters and used to clear the minefields and blow up unexploded projectiles, which endangered civilian lives.
During the battle of Odessa, the pioneers were used for the first time according to German doctrine as assault troops against fortifications. They used different explosive charges to create gaps in barbwire nets, to clear minefields and to blow up pillboxes. They also had hand grenades, Molotov cocktails, smoke grenades and Pignone model 1937 flame-throwers.
The experience gained in the 1941 campaign determined a reorganization of the pioneers. The new pioneer battalion was identical for the infantry, mountain, armoured division and corps. The former worker-pioneer doctrine (French) was totally replaced by the assault-pioneer doctrine (German). The 2nd and 3rd companies were similar to the infantry companies. They also had a mortar platoon (3x81.4 mm mortars) and tank hunter squad equipped with 3 AT rifles (captured PTRD or PTRS). A command company was added. It consisted of a machine-gun platoon (4 MGs), an AT gun platoon (3x47 mm pieces) and a communications platoon. The battalion was also equipped with special weapons: explosive charges, assault decks, flame throwers etc.
During the fights in the winter of 1942-43, the pioneers had to take part in the desperate attempts to halt the Soviet advance, just like the regular infantry. From 1943 onwards, this became a frequent practice in the Romanian Army. In 1944 things came back to normal and the pioneers returned to their specific tasks.
By 1943, there were 8 road-building battalions (1st-8th) and a few road detachments, which were working east of the river Dniester.
In the autumn of 1943 was created the Mountain Pioneer Group at Brasov. It was mainly a training unit. The same year, the Motorized Pioneer Battalion was transformed into the 8th Motorized Pioneer Regiment.
In 1943, the pioneer regiments were reorganized into 2 types: A and B. The A type had two pioneer battalions (3 companies of 3 platoons) and a specialist battalion made up of one specialists company (2 flame-thrower platoons and one communications platoon), one machine-tools company and one motor company. The B type regiment's battalions had only 2 companies (of 3 platoons) and the specialists company had only one flame-thrower platoon and no machine-tools platoon.
In 1943 the pioneers received imported German equipment: model 1924 grenades (offensive and defensive), Flammenwerfer 35 and Mittlerer Flammenwerfer, smoke grenades, mines, mine detectors (Berlin 40 and Köln), Seddin pneumatic boats and others. The Romanian MAN model 1941 mine detector also entered service that year.
In the summer of 1944, the 5th and 8th Road-building Battalion were put at the disposal of the 4th Corps and of the 4th Army.
After 23 August 1944, a battalion was created from the different training units behind the front. It participated in the fights with the German forces until the new front line was established.
In October 1944, according to the armistice protocol, the number of pioneer units was reduced. The 1st Pioneer Regiment was attached to the 5th Territorial Corps, the 3rd Regiment was disbanded and the 5th Regiment was assigned to the 4th Corps. The 4th Regiment was transformed into the 4th Railroad Regiment and the 8th Motorized Pioneer Regiment was merged with the Pioneer Training Center.
Because of the losses on the Moldavian front (mainly prisoners taken by the Soviets after the armistice), the divisional pioneer battalion was reduced to a company (a squadron for the cavalry). They had the number of the infantry division (2nd, 3rd, 4th, 6th, 9th, 11th, 18th, 19th and 21st). For the mountain divisions were the 38th for the 2nd and 39th for 3rd Mountain Division. At the disposal of the 1st and 4th Armies were the 30th and 31st Pioneer Companies.
The 1st, 3rd, 4th, 5th and 8th Road-building Battalions were put at the disposal of the 2nd Ukrainian Front (in which were incorporated the Romanian armies) with the mission to secure the communication ways in Hungary and Czechoslovakia.
The corps pioneer battalion had two identical pioneer companies (3 pioneer platoons and one mortar platoon), a command company (communications platoon, machine-gun platoon and AT platoon) and a battalion train. A divisional pioneer company had the same structure as a company from the pioneer battalion.
Even with reduced numbers the pioneers had an essential role in the last months of war, contributing to the success of the operations against Germany.