At the beginning of 1941, there two railroad regiments (1st and 2nd) subordinated to the Railroad Brigade, as well as to guard battalions (1st and 2nd). On 1st May 1941, the Railroad Detachment Command was created.
The 1st Regiment was made up of the 1st Railroad Operation Battalion (1st-3rd Railroad Companies), the 2nd Railroad Operation Battalion (4th-6th Railroad Companies), the 3rd Railroad-building Battalion (7th-9th Railroad-building Companies) and the 4th Narrow Railroad and Bridge Battalion (10th, 11th, 13th Bridge Companies and 14th Narrow Railroad Company). In June, the regiment also mobilized the 1st Narrow Railroad Company and the 15th Bridge Company.
The 2nd Railroad Regiment had 6 battalions: the 3rd Railroad Operation Battalion (1st-3rd Railroad Companies), the 4th Railroad Operation Battalion (4th-6th Railroad Companies), the 3rd Railroad-building Battalion (7th-9th Railroad-building Companies), the 4th Railroad-building Battalion (10th-12th Railroad-building Companies), the 2nd Narrow Railroad Battalion (13th and 15th Narrow Railroad Companies) and 2nd Railroad Bridge Battalion (21st and 22nd Railroad Bridge Companies).
The railroad operation company had one engine platoon, one train platoon, one maintenance and destruction platoon, one station platoon and one guard platoon. The railroad-building company had one technical platoon, three railroad-building platoons, one battle train and one regiment train. The two railroad guard battalions consisted of 10 guard companies (1st-10th) each.
In November 1941, the 1st Regiment organized to detachments: Tighina (6th Railroad Operation Company, 13th Railroad-building Company, 21st and 23rd Railroad Bridge Companies) and Arciz (7th, 8th and 12th Railroad-building Companies and 22nd Railroad Bridge Company), which were going to be used in Bessarabia and Northern Bucovina.
On 10 February 1942 three more guard battalions (3rd-5th) were raised and on 22 February the Railroad Guard Battalion Group was created.
On 1st July 1942, the 3rd Railroad Regiment was created and the other two were reorganized. All three had an identical structure: 1st Railroad Operation Battalion (1st-4th Companies), 2nd Railroad-building Battalion (5th-10th Companies) and 3rd Railroad Bridge Battalion (11th and 12th Companies).
By 1944 there 22 railroad work detachments mobilized, subordinated to the Railroad Detachment Command. They were the 46th-59th, 62nd-65th, 67th, 68th, 105th and 107th Detachments. Each had between 2 and 7 companies.
In 1943, the railroad units received a new mission: to destroy the railways and bridges in case of retreat. In this operation were involved 13 companies (4 operation, 6 building and 3 bridge companies).
On 15 November 1943, the railroad troops were again reorganized. The three regiments had a similar structure: the 1st Railroad Operation Battalion (4 companies), the 2nd and 3rd Railroad-building Battalion (3-6 companies each) and the 4th Bridge Battalion (2-3 companies). The 2nd and 3rd Regiment also had a training battalion (4 companies). Also, two more railroad guard battalions (6th and 7th) were created.
In October 1944, the 4th Pioneer Regiment was transformed into the 4th Railroad Regiment. Also, the Railroad Brigade's Operations Group was formed. It was made up of the 3rd Regiment, the 4th Bridge Battalion from the 2nd Regiment and the 13th Telephone and Telegraphy Company. The group was assigned to the Railroad Command of the 2nd Ukrainian Front and followed the Romanian troops in the Hungarian and Czechoslovakian campaigns. The rest of the units that remained in Romania were used to rebuild the railways destroyed during the military operations on Romanian soil.