In early 1941, the Border-guard Corps was made up of eight regiments (numbers 1st through 8th) organized in four brigades (numbers 1st through 4th), deployed on the frontiers, and a group of border-guard ships (7 patrol boats, one tug boat, one transport barge and one barracks barge), which was based in Braila.

The regiments were stationed in the following areas:

• 1st Border-guard Regiment – Bucharest (on the Bulgarian border)
• 2nd Border-guard Regiment – Cernavoda (on the Bulgarian border)
• 4th Border-guard Regiment – Deva (on the Hungarian border)
• 7th Border-guard Regiment – Sibiu (on the Hungarian border)
• 3rd, 5th, 6th and 8th Border-guard Regiments on the border with the Soviet Union

Although four brigades existed, the border-guard regiments usually operated as independent units, subordinated directly to the territorial corps in their area or to the Border-guard Division while on campaign.

A border-guard regiment was structured somewhat different from a 1941 infantry one: 3 battalions, but one was for training, not for campaigning. Each battalion was made up of two rifle companies and one heavy weapons company. There was also one horse-mounted platoon for each regiment (numbers 1st through 8th).

The 1st, 2nd and 5th Regiments were united to form the Border-guard Division, which was assigned to the 5th Corps of the 4th Army. The Division also incorporated the Border-guard Artillery Regiment, which was made up of two battalions: one equipped with 75 mm guns and the other with 100 mm howitzers. The total strength of roughly 10,000 was inferior to that of the infantry division. The equipment was also inferior to the one of the regular infantry. They used older rifle models like the Mannlicher model 1893 and 1895 and Schwarzlose machine-guns and had fewer AT guns. However, the extended time of service and the habitude to operate in smaller units created a force with higher initiative than the regular infantry. The performance of the Border-guard Division during the 1941 campaign confirms its higher standard.

The losses of the border-guards were very high though, almost equaling the numbers they went into battle with, which means that replacements were probably drawn from the other regiments as well (see for example the photo attached to this article of the two officers from the 3rd Border-guard Regiment KIA in September 1941, although their regiment was on Romanian soil then). The Border-guard Division was pulled out of the front line in early October, before the fall of Odessa. It returned to Bucharest on 20 October 1941 and its regiments resumed their usual duties on the frontiers.

In the summer of 1942, four regional battalions designated "Bihor", "Vrancea", "Neamt" and "Bucovina", after the regions they served in, were created along the border with Hungary. Each had 28 officers (all reservists, with the exception of the commanding officer), 34 NCOs and 709 soldiers. The recruits were all locals that haven’t been called up in the regular units from those areas, usually elder citizens. They were equipped with rifles, 12 machine-guns, 24 light machine-guns, 6 small caliber AT guns and 12 mortars. This was the situation on paper. In reality most of the heavier weapons lacked. The drills and training took place every Sunday morning for six hours. In 1943, the number of battalions was increased to nine, with the formation of the "Aries", "Somes", "Cluj", "Codru" and "Cris" battalions. They were split into two groups according to geographical criteria: "Aries", "Somes", "Cluj", "Codru" and “Bihor” in the Transylvanian Group and "Vrancea", "Neamt" and "Bucovina" in the Moldavian Group. Some elements of the “Bucovina” Fixed Regional Battalion became the first anti-communist partisans following the occupation of the region by the Soviets in early 1944. But these units proved their utility during the skirmishes with Hungarian forces at the end of August and in September 1944, when they contributed to the delaying of the Axis advance, allowing for the bulk of the regular Romanian Army and the Red Army to cross the Carpathian passes.

For less than a year, from April 1942 to March 1943, another division was organized using the border-guards regiments as its core: the 2nd Guard Division. These were the 2nd, 3rd and 4th Border-guard Regiments (the 2nd Regiment also appears on the roster of the Border-guard Division during this period). The division never saw action and was used to fill up the ranks of some of the divisions decimated near Stalingrad during the winter. The 18th Infantry Division was turned into the 18th Mountain Division using border-guards as reserve mountain troops. This was another indication of the higher standard of the border-guards when compared to the regular infantry. However, this mountain division wasn’t on par with the older ones in terms of proficiency and was later downgraded to infantry division.

On 1 May 1943, the Border-guard Division was also disbanded and its troops were used to reorganized the 4th Infantry Division that had been depleted in Russia in 1942. The 5th Border-guard Regiment merged with the 21st Infantry Regiment, the 1st Border-guard Regiment with the 20th Dorobanti Regiment, the 2nd Border-guard Regiment with the 5th Dorobanti Regiment and the 2nd Border-guard Artillery Regiment with the 2nd and 10th Artillery Regiments. However, the same year two new border-guard regiments were created: the 9th (Timisoara) and 10th (Brasov), which made up the also new 5th Border-guard Brigade.

In the spring of 1944, the 1st Artillery Battalion of the remaining Border-guard Artillery Regiment was transformed into an AT Battalion equipped with the 75 mm Resita model 1943, being the second unit in the Romanian Army to receive the new weapon. It was supposed to act as an independent unit. Later on, the entire regiment was converted to the antitank role and it fought on until the end of the war in Hungary and Czechoslovakia.

After 23 August 1944, the border-guards participated in the fights with the German and Hungarian troops on the Western frontiers, slowing down the enemy advance until the regular units could cross the Carpathian Mountains. After Northwestern Transylvania was retaken, at the end of October 1944, the Border-guard Corps was reduced according to the armistice protocol signed with the Allies. The 4th, 6th and 7th Regiments were disbanded. Almost half a year later, in the spring of 1945, the 2nd, 3rd and 5th Border-guard Regiments had the same fate. A part of the former border-guards were used to fill in the ranks of the different units on the front, especially those of the 2nd and 3rd Mountain Divisions.

The Border-guard Corps was renamed the Border-guard Command and was reduced to only 4 regiments (1st, 8th, 9th and 10th) and the Border-guard Naval Company. There were around 12,000 men in total. On 12 June 1947, the border-guards were transferred to the Internal Affairs Ministry, cutting the ties with the Army.