The following chain of thoughts started when a strange place name appeared in a blog post by Swedish defence blogger Jägarchefen. Further research led to a theory, the reasoning behind which is detailed below.
The CIA file
The open archive of CIA FOIA files include a large number of documents dealing with Soviet vessel movements in the Baltic Sea. Most of these are rather unspectacular, doing little but dispelling the idea that intelligence work is anything like a Bond-adventure. There are however exceptions, like file number CIA-RDP80-00810A007600280010-0, dated 13 October 1955.
‘Kalbod Shallows light’ likely refers to Kalbådagrund lighthouse southeast of Helsinki, where a caisson-type lighthouse was erected on a dangerous shoal in 1952. Here, a flotilla of 10 to 12 midget submarines passed by under tow in the evening of 27 May 1955. But where did they come from, and why were they outside of Helsinki in 1955?
The War Trophies
In the closing years of World War II the surface units of the German Navy faced pressure from ever increasing numbers of Allied aircraft and naval ships. The logical answer was to start using the submarine force also for missions closer to shore. This called for smaller vessels, capable of manoeuvring in the more confined waters of the Atlantic coastline.
Probably the most successful of the host of different craft created was the Typ XXVII B, better known as Seehund. The 12 meter (~40 feet) long submarine had a crew of just two man, and as opposed to most midget submarines it wasn’t fitted for operations with limpet mines or divers, but was armed with two G7e torpedoes, the standard weapon of the German submarine force. As the submarine was so small, these were strapped on externally. They were sighted through a fixed periscope, located in the forward part of the tower.
The Soviet captured a number of these vessels, though exactly how many remains unclear. Some sources claim that only a very limited number was in use, but most list a significantly larger force. The British Royal Navy’s Director of Naval Intelligence in 1952 commented that the Soviet Navy “acquired some 50-70 ex-German, Italian and Japanese midget submarines after the war, but it seems likely that they have produced their own post-war version, which, from reports, seems to incorporate parts from the design of all above. There are also reports which indicate training in midget S/Ms in the Soviet Navy at the present time.” The CIA is also looking at a similar number, stating that the Soviet Navy had “at least 70 midget submarines” in service in November 1953, of which around 20 are ex-German Seehund vessels, the rest being an “improvement on the previous type and made use of German SEEHUND plans”. These Soviet improved Seehunds were built after 1947. Notable is also that CIA has no information “regarding specific bases for these submarines”, but they also concede that they can be operated from “any existing base”, or from a properly equipped support ship.
Other sources support this picture. The Swedish intelligence service was also on the trail, with the so called T-office reporting in 1946 that “On pier in Kronstadt harbour lies some midget submarines, probably ex-German”. Russian naval historian Vladimir Shcherbakov notes that the Seehunds “were used rather intensively”. Swedish historians von Braun and Gyllenhaal puts the confirmed number of complete Seehunds captured as “at least two”.
But how did the Soviets manage to build up a sizeable force from war trophies and modified designs?
The majority of the Seehunds were built at Schichau-Werke in what was then Elbing in East Prussia (today the Polish city of Elbląg). The yard escaped relatively unscathed during the war and the immediate post-war, and in 1947 it was one of few factories listed as being in service, having just delivered the first new built vessels postwar (these being torpedoboats). In the same year, it was reported that Soviet (and Polish) companies tried to recruit former “technicians, employees, and workmen” of the yard in East Germany. Most refused, but “a certain number” accepted and left for East Prussia, presumably to work at the former Schichau subsidary at Contienen, which had produced parts for submarines and minesweepers during the war. The Contienen yard as well was reported to have seen relatively little damage during the war, and escaped dismantling after the Soviet forces occupied it.
In 1949, the operations at Schichau-Werke in Elbing was reported to have risen back to 80 percent of its wartime capacity. Around 120 German prisoners of war were still employed as “skilled workers”, pointing to the fact that the earlier attempts to recruit workers hadn’t produced enough volunteers. The yard featured a modern welding current distribution system, and an expansion program of the yard was planned, the aim being to double the capacity by spring 1951. Interestingly, the CIA file reporting this includes a comment that the recent information “essentially confirms” other information on the shipyard, and that “it appears likely that no vessels other than small submarines are now being constructed there”.
To remember is that during the last six months the yard was in operation during the war, the number of Seehunds produced in Elbing seems to have been over 100. If the CIA report was correct, even at 80 percent production the yard would have built 50 new vessels in a matter of months. But where did they go?
When the Continuation War ended, amongst the Soviet demands was one which prime minister Paasikivi described as “horrendous”. The Porkkala peninsula was to be leased to the Soviet Union for 50 years, i.e. until 1994.
This replaced the earlier deal under which the Soviets had leased the Hanko peninsula further west after the end of the Winter War, and included a very favourable transit agreement. Under this, the Finnish customs authorities had no right to inspect the cargo holds of trucks or trains transiting between the naval base and the Soviet mainland. Soon it became apparent that foul play was involved, as sometimes the trucks could make the trip in four hours, while sometimes the time on the road stretched to up to ten hours. A SIGINT station for listening to Finnish radio communications was created at the Majvik mansion, today a meetings and convention hotel, and suitably located on top of a large hill close to the shore. In the early 1950’s the station was manned by 24 NCOs and four officers, working in three shifts to maintain a constant surveillance of the Finnish radio networks. The station was not part of the naval base’s chain of command, but instead reported directly to the intelligence section of the Leningrad Military District in all matters.
In addition to being a naval base, the most well-known vessel of which was the monitor Vyborg (former Finnish coastal defence ship Väinämöinen), the base also played a significant role as an intelligence hub. A number of arrests were made and dead drops uncovered in connection to the transit traffic mentioned above, including that of air force captain Martti Salo of the aerial photography unit in Tikkakoski. It appears that the main responsibility for intelligence gathering in Finland was placed upon GRU, likely in part due to the heavy use of the military trucks travelling to and from Porkkala.
Amongst the most important units of the bases was its intelligence unit. In a report covering the third quarter of 1945, the unit had not only counted and identified the nationality of all vessels sailing past the base (1 371 vessels in total), they had also, as a collaborative effort between the “officers of the base’s staff and units situated in Finland”, gathered information and systematically categorised this into a file covering multiple aspects of Finland, including:
- Much information on the Pansio naval base
- Information on the Army and Coastal Artillery units located in the Turku region
- A description of the oil depot being built in Naantali
- A description of Finland’s coastal defences
- Information regarding the Finnish coast guard and all its bases
The information gathered also went down to the individual level, covering 96 Finnish officers, including their service records and personal evaluations.
The continuous building of trenches and bunkers as well as the naval activity came to an abrupt halt in 1955. In September, Khrushchev suddenly informed Finland that the base would be returned. This doomed the heavily fortified base, and all defensive works were demolished, including the almost-finished command bunker Los which stretched over 100 meters through the mountainside. The personnel, numbering over 15,000, was transferred away, as was the tens of naval vessels and small crafts that were stationed there.
But did the intelligence gathering extend to other methods as well?
My theory is that the convoy sighted on an easterly heading south Helsinki in May 1955 indeed did consist of Seehund-type submarines (either ex-German or modified new-builds). I further believe that they were in transit from Porkkala naval base to Kronstadt, either due to a unit transfer (possibly due to having received early notice of the upcoming closure) or after a finished exercise/mission.
In other words: in addition to the surface and land-based units known to have been stationed there, Porkkala played host to a unit of midget submarines in the first half of the fifties.
These have been either exercising or permanently stationed there. Considering the unique nature of the Finnish archipelago, it isn’t far-fetched to conclude that any exercises held there were made with an eye towards either the Finnish or Swedish coast. Furthermore, considering the extensive intelligence work done by the GRU out of Porkkala, it is likely that the submarines would have participated in covert intelligence gathering against Finnish targets. Especially as the intelligence work is known to have in part been directed against naval and other coastal sites
Are there alternative explanations? Certainly. The submarines might have been misidentified barges, or they might have come from Tallinn and turned north to get around heavy weather. However, the most likely explanation in my opinion is that the vessels were transiting from Porkkala to Kronstadt:
The sketch captures the general outline of the Seehund well, including the approximate location and general shape of the conning tower and the location of the fixed periscope. Riding high would be explained by the lack of torpedoes, which are unlikely to have been carried during transit.
It is assumed that the Soviet Navy operated a number of Seehund-type submarines, including of an improved design. The Soviets did capture one of the main production sites of the Seehund, and this resumed operation relatively soon after the war, with part of the workforce being German. The ability to produce the improved design appears to have been there.
The Seehunds were sighted in Kronstadt, as well as in other parts of the Baltic Sea during the time frame in question.
Porkkala held an important dual role as a naval base and intelligence gathering hub. The later was led by GRU, with some units being directly subordinated to the Leningrad Military District. Amongst the targets for the intelligence gathering operation were Finnish Navy, Coast Guard, and harbour locations. Using midget submarines for covert intelligence gathering would fit that pattern.
The location in the northern half of the Gulf of Finland also seems more likely for a unit coming from a Finnish port than from a location on the southern shore of the Gulf.
A special ‘Thank you’ to Jägarchefen and Lars Gyllenhaal!
 Register No. P.D. 054/52
 CIA file CIA-RDP80-00810A002800340004-3
 All quotes in paragraph from: J. von Braun and L. Gyllenhaal, Ryska elitförband och specialvapen, 2nd edn., Stockholm, Fischer & Co, 2016
 CIA file CIA-RDP82-00457R001100020007-4
 CIA file CIA-RDP82-00457R000800070004-6
 CIA file CIA-RDP82-00457R003300540006-7
 J. Leskinen, ‘Porkkalan tukikohta 1944-1956’, in J. Nieminen (ed.), Porkkala – Tapahtumien keskellä, Maanpuolustuskorkeakoulun Sotahistorian laitos, 2009
 K. Rentola, ‘Porkkala ja tiedustelu’, in J. Nieminen (ed.), Porkkala – Tapahtumien keskellä, Maanpuolustuskorkeakoulun Sotahistorian laitos, 2009
 L. Amirhanov, ‘Neuvostoliiton Porkkala-uddin laivastotukikohta kylmässä sodassa 1945-1956’, in J. Nieminen (ed.), Porkkala – Tapahtumien keskellä, Maanpuolustuskorkeakoulun Sotahistorian laitos, 2009