The Border Defence Regiments were formed from the mobilized men in 1944.From late 1943 with a pool of new OK recruits, OK cadres and volunteers, german Orpo succesfully formed 6+1 Grenzschutz-Regimenter: again a very hard effort for OK; but this effort was not the last one.
Here's some additional information about Estonians in German army.
In the summer-autumn of 1941 there was formed five Sicherungsgruppen in the 18th Army: nr. 181-185. The men were volunteers. In Narva there was the Ersatz Sicherungsgruppe. In February 1942 also the 186th Sicherungsgruppe was formed. It did not achieve full strenght and wasn't sent to the front. In autumn 1942 it was disbanded and men sent to the reserve group in Narva. Two companies from the Estonian groups acted independently: companies nr 13 (183th Group) and 17 (184th group). On 1st May 1942 the Estonian Sicherungs units had 4050 men. By the beginning of November 1942 the Sicherungsgruppen were formed into Ostbattalions nr. 658, 659, 660 and Ostkompanie nr. 657 (former 13th Sicherungs company). In Narva the reserve unit also was renamed accordingly. On 1st August 1943 the Estonian Ost Btls were given under Waffen-SS but this institution wasn't really interested in them. In April 1944 on the base of the 660th Btl the 3rd Btl/46th SS Rgt was formed. On the base of 658th Btl the 1st Btl/47th SS-Rgt was formed and on the base of 659th Btl the 2nd Btl/47th SS-Rgt was formed. The 657th company was divided between the units of 20th SS-Div.
AG "Nord" formed in 1941 from volunteers several Schuma units: Estnische Schutzmannschafts-Abteilung Dorpat, Fellin und Poltsamaa (in the beginning of 1942 the units recieved numbers 37, 38, 39 and the name Sicherungs Btl). Also a Bau-Abt (from the beginning of 1942 42nd Sich Btl) was formed and a reserve abt in Tartu (from the beginning of 1942 the 41st Sich Btl). SD formed the Pleskov Schutzmannschaft (from the beginning of 1942 the 40th Sich Btl). The units (except the reserve units) were in action in Russia. In 1943 the Sich Btls were subordinated to the Orpo and the name Polizei Battailon was started to use. In 1943 the 39th Btl was disbanded, men were given into 3rd SS-Brigade and 287th Polizei Btl. The 37th, 38th and 40th Battalions were sent to the Daugavpils area in July 1944 as the 2nd Estonian Police Regiment. In August the regiment was disbanded. 37th and 38th Btl were sent to the Tartu front. 40th Btl was disbanded in August and men were given to other units. The memebers of these battalions, which arrived later Germany, were given into the 20th SS.
In autumn 1941 the SS and Polizei Führer in Estonia gave the order to form Wacht Scutzmannschaft Battailons. The men were volunteers. The 29th Btl was at first in guarding duties in Tallinn, then in March 1942 was sent to the Leningrad front, where it was until January 1943. Then was brought to Estonia and disbanded due losses and because many had left to the Estonian Legion. The 33rd Btl was sent to the Leningrad front at the beginning of 1942 where it remained until December 1942. Then it was disbanded in Estonia. The 30th, 31st and 32nd Btls were probably formed in 1942 and disbanded by January 1943. Probably they didn't achieve full strenght and were located always in Estonia. The 34th Btl was disbanded already in 1942 and the men were given into the 36th Btl. The number 34 was given to an another Estonian unit which had been in Org "Todt". The 35th Btl was formed at the beginning of 1942, but soon the men from this unit were sent to the 33rd Btl. In spring 1943 part of the men from the disbanded 33rd Btl were transfered to the 35th Btl and it was renamed as the 35th Reserve Schutzmanns. Btl. It was then located in Tallinn and in the end of summer 1944 was evacuated to Germany. The 36th Front Schutzm. Btl. was formed from the end of 1941. In 1942 sent to Belorussia, then in Ukraine guarded POWs, then to the front near Stalingrad and lost there 39 KIA, 97 WIA, 11 MIA. In the beginning of 1943 it was transported to Estonia and was disbanded.
By August 1942 in the Org "Todt" there were six Estonian companies (volunteers) - 1000 men - in the area of Pskov. Four of these companies were subordinated to OT Estonian Defence Commando. They secured the construction works against partisans. In 1942 the commando was renamed into 34th Scutzmannschaft Front Btl and subordinated to Orpo. It seems that the unit was also renamed into 34th Police Btl.
Under the Kriegsmarine there was Estonian Coast Defence Rgt. Formed from volunteers in autumn 1941 and disbanded in the spring of 1942.
In Germany in 1941 was formed Polizei Btl "Ostland" (from the beginning of 1942 - 304th Polizei Btl) which included Estonians (two companies) and Latvians (one company) who had gone to Germany in 1940-41. By September 1943 all the Estonians were removed this unit.
In a previous post I have mentioned already the battalions formed from Omakaitse (nr. 29-33). Since they were subordinated to Orpo their title was Polizei Btl. The 30th Polizei Btl participated in battles on the Narva front until March 1944, then it was on the coast guard. Also the 31st and 32nd Btls were on the Narva front. The 33rd Btl participated in battles against the Soviet landing in Mehikoorma area (January 1944). The battalions nr. 30-33 were disbanded in summer 1944 and the men were given into 37th, 38th and 40th Polizei Btl. It seems that the 29th Btl was completely destroyed on the Narva front in February 1944.
In 1943 and at the beginning of 1944 several police units were formed (at first named as Schutzm Btls but in December 1943 all were renamed into Polizei Btl). 286th Btl formed from field police in May 1943. It got also men from the disbanded 36th Front Schutzm Btl. In autumn fought against partisans in Poland and Belorussia then at fought at the Nevel front. About 200 men returned to Estonia and then got back their former posts. The battalion was after that manned with mobilized men and was used in coast-guard. Most men remained in Estonia during the German retreat. 287th Polizei Wacht Btl was formed from the men of 33rd, 36th Schutzm Btl, 39th Sich Btl and Estonians who deserted from the Red Army at Velikie-Luki (over 1 800 Estonians from the 8th Estonian Rifle Corps were captured there - mostly deserters). Later also mobilized men were sent to this unit. The btl guarded different objects (including POW and KZ camps). The btl was evacuated to Germany and the men given into 20th SS. 288th Polizei Füsilier-Battailon was formed in 1943 from the men of several disbanded units and from mobilized men. In September the btl was in Vilno then fought against the partisans in Belorussia. Later in Estonia had coast-guard duty and largely remained in Estonia. There is little information about 289th, 291st, 292nd Polizei Füsilier-Battailons. It seems that they were at the Narva front in 1944. Nothing is known about the 290th and 293rd Polizei Btl.(were they even formed at all?). 286th, 288th, 291st and 292nd btls were subordinated to the 1st Estonian Police regiment in April 1944. The regiment had coast-guard duty (Gulf of Finland in the Narva area). By July the regiment was disbanded and on the basis of the staff the staff of the 2nd Estonian Police regiment was formed.
I have found also a mention of the1st Estonian SS Special Company.
In 1944 five Construction-Pioneer Battalions were formed from Russians who were citizens of Estonia in 1940. The members were mobilized.
There was also the SD 1st Special Battalion formed from Estonians. It is known that at the end of 1943 it fought against partisans in Belorussia.
In February 1944 seven border defense regiments were formed (1-6 and Rgt "Tallinn"). Rgt "Tallinn" (2007 men) was sent to the Narva front on 13th February (later disbanded and men sent to the 20th SS). There was also training-reserve regiment for the BD regiments (on 1st April renamed into 1st Estonian SS-Reserve Regiment).
The Estonian units on 1st April 1944 (the list obviously is not complete and it doesn't include most of the Omakaitse):
20th SS-Division - 5 000 men (the estimation is for May 1944)
The reserve units of the 20th SS-Division in Klooga - 9 157 men
Rgt "Tallinn" - 1 647 men
1st Border-Defence Rgt - 2 501 men
2nd B-D R - 2 520 men
3rd B-D R - 2 646 men
4th B-D R - 2 152 men
5th B-D R - 2 386 men
6th B-D R - 2 577 men
1st Estonian SS-Reserve Rgt - 2 986 men
Major J. Lääne's training unit in Tartu - 585 men
Reserve units by the staffs of the Omakaitse in Viljandi, Tartu and Pärnu (subordinated to the 1st Estonian SS-Reserve Rgt) - 4 372 men
Police Battalions nr 29-34, 37, 38, 40, 42 - about 4 000 men
286th Police Btl - 692 men
288th Police Btl - 198 men
289th Police Btl - 600 men (estimation for 1st March 1944)
SD 1st Special Battalion - 500 men (estimation for 1st March 1944)
Three SD training companies - 400 men (estimation for 1st March 1944)
Jagdkommandos - 612 men
Custom Border Defence Btl nr. 43-45 - 600 men (estimation for 1st March 1944)
Four construction-pioner battalions - 2 361 men (Russians actually)
Estonian air units and flight school - 700 men (1st March 1944)
35th Reserve Battalion - 400 men
41st Reserve Battalion - 600 men (1st March 1944)
Btl "Narva" - 100 men
Ost Battalions nr. 658-660 - 800 men
Other smaller units and services - about 1 000 men
Alltogether about 52 000 men and it seems taht this number doesn't include wounded in hospitals. Also it doesn't include most of the Omakaitse.
