The history of the Finnish defensive fortification lines against Russia starts with the declaration of independence of Finland in 1917. The Bolsheviks basically let Finland go, presumably due to having too much trouble on their hands to bother trying to keep hold of the splinter of Russian Empire which had never been even remotely Russian to begin with. Despite the generous gesture, relations between newborn Soviet Russia and Finland remained tense. An extremely bloody civil war erupted in Finland, just as it did in Russia; but unlike in Russia, even with Soviet support, the Reds in Finland were brutally crushed. Moreover, it was Finland which then initiated military intervention in various parts of Russian Karelia, hoping to sway Karelian people (closely related to the Finnish) to join their country. The intervention, known as "Kinship Wars" in Finland, was rather minor in scale and ultimately the Karelians turned out to be apathetic about the whole thing, but nonetheless that was one more reason for Soviet Russia to be on not very friendly terms with Finland.
Thus the idea of the Mannerheim Line was born. It was not what it was really called at the time, but it was indeed commissioned by Field Marshal Mannerheim, the famed Finnish commander-in-chief throughout the interwar period and the World War II. The line was meant to be a contiguous line of fortifications, including concrete bunkers, dragon's teeth, barbed wire, and natural features such as lakes and impassable swamps. It stretched across the entire Karelian Isthmus, from Humaljoki (Yermilovo) at the coast of the Gulf of Finland to Taipale (Solovyovo) at the coast of the Ladoga Lake.
It's a common knowledge now that the Mannerheim Line turned out to be a great success in the Winter War of 1939-1940. Soviet offensive was halted by the line for several months, and suffered great losses. This was particularly noteworthy because the line itself was frankly by no means a marvel of fortification. It had been constructed over the previous twenty years, mostly very slowly, cheaply, and shoddily, with rather small bunkers of unreinforced concrete. Few people really believed the line would actually end up being utilized. Only by 1938, when the war already seemed imminent, works on the line intensified. In the end the Mannerheim Line was broken through, but given sheer numbers of the Soviets, that was probably bound to happen anyway. Mannerheim later claimed that the success of the line was more due to the morale and valor of the Finnish troops than anything else.
The Winter War ended in 1940, but it was clear to everyone that a much larger war was at the doorstep. Finland allied itself with Nazi Germany, having, practically speaking, not much choice in the matter. Allying with the Soviet Union would likely mean sharing the fate of the recently annexed Baltic countries; and even if Finland remained indepentent, it would have been trivial for Germany to blockade it from the sea. And as Winter War showed, Allied nations were not particularly eager to help Finland with anything but lip service.
Thus Finland had to prepare itself for an even larger war in very short time (it helped that its economy was already militarized after the Winter War, and the martial law was never officially revoked). And since the Mannerheim Line, with all its shoddiness, worked so well, why, it was obvious that they just needed to build an another line, and do it properly this time!
The Salpa Line (Salpalinja, Finn. Bolt Line or Padlock Line) absolutely dwarfed its predecessor, stretching from the Gulf of Finland in Virolahti, along the entire 1200 km long new Soviet border, to Petsamo at the Arctic Ocean. 35,000 workers, both volunteers and conscripted men ineligible for war, and additionally 2,000 women, worked on the line by the spring of 1941. The line remains the largest construction project of Finland ever to this day. It is estimated to have cost 2.5 billion Finnish markka, which sounds appropriately impressive, but sadly I could not figure out how to adjust this sum for inflation; for what it's worth, it took 5% of the entire Finnish budget at the time. The line had 728 concrete bunkers, 130 km of trenches, 315 km of barbed wire, and about 350,000 of stone blocks used for dragon's teeth and the like. Old guns from the 1800s and trophy weapons from the Winter War were used in some bunkers. As with the Mannerheim Line, Salpa Line actively employed natural terrain features, such as the massive lake maze in the Southeast of the country. Overall, it was not as impregnable and advanced as the Maginot Line, but still quite a feat of engineering.
As is often the case with modern super-expensive weaponry and the like, the Salpa Line ended up never actually used. Most of the fighting of the Continuation War of 1941-1944 took place on Soviet territory, where more defensive lines (VT-Line and VKT-Line) were hastily built on the Karelian Isthmus. Not a single shot was fired over the Salpa Line itself. However it still helped the Finnish to have a significantly stronger bargaining position in the peace talks.
Thus the Salpa Line remained undamaged (in stark contrast with the Mannerheim Line which can now be seen only as heaps of concrete rubble overgrown with moss and deep into the isthmus woods), and, due to high quality of its constructions, remains in a very good condition up to this day. It is the last major defensive line of this kind ever constructed; subsequent arms developments made such lines much less effective. Following the end of the Cold War, all its fortifications were open to public. A few museums were subsequently opened to make the line more accessible to the public, but many more bunkers and the like can in principle be visited by a determined hiker on his own.
Driving through Virolahti on Road 7 towards Helsinki, you might have noticed two brown signs towards Bunkkerimuseo and Salpalinja museo. The second museum, simply known as Salpa Line Museum, is the larger one, and the one I visited on my trip.
1. The museum is located in just about 20 kilometers from the Russian border at Vaalimaa. Turn right onto Regional Road 384 in Virojoki, and turn left following the route of the same Road 384 in the middle of Miehikkälä village (the village is actually named Saivikkala but this name is hardly ever mentioned). In a few kilometers you'll see a sign for the museum parking lot. The museum is located in Miehikkälä Municipality, and is probably its only significant attraction. The municipality population is 2,100.
The main museum building, pictured here, has an indoor exhibition, but I'm going to focus on the outdoor one. Numerous signs warn that you still need to buy a ticket even for the outdoor exhibition, although this is not physically enforced. The ticket costs some quite reasonable €8. You also get a leaflet with a map of the exhibition, with texts in English and Russian. The map suggests a few walking trails, but I chose to combine parts of them and ended up seeing virtually everything the museum has to offer.
Incidentally, this is the museum website. Note the opening hours. Like most rural and/or remote museums in Finland, the museum is normally open only from May to September; special arrangements are required in other months.
2. I must start by mentioning I'm by no means a military history buff. I'm sure some people can recognize the things I about to show at a glance, and write an essay on every single on of them, but I had to make do with information from the leaflet, the information tables (mostly unintelligible due to being in Finnish as usual), and whatever I managed to Google. For example, this is a gun. I'm pretty sure it is. I think this is one of the older guns of Russian Empire era, but I didn't keep any notes on this particular gun. I think it's supposed to have large wooden wheels, but apparently they were taken off for restoration.
3. Bunkers of the Salpa Line varied in size. Apart from full-fledged pillboxes with guns and a degree of autonomy there were small shelters, which apparently were casted in concrete in one go using a similar cast form.
4. Some gas cannisters nearby. I'm not sure of their purpose.
5. Trenches form a rather dense network here at the site of the museum. Some of them are dug in the dirt and reinforced with wood, while others are simply cut into the bedrock which is commonly exposed here, typical of Southern Finland.
6. The museum is entirely located in a bright pine forest, looking especially cheerful in this September noon. Ripe berries hang right over the trenches.
7. Another trench.
8. Overlooking the Road 384 is a rocky hill with a wooden observation tower on top. The tower was supposed to be used for anti-air defense.
9. Trench network in front of the hill.
11. At the top of the tower. Endless pine woods stretch in every direction until the horizon. The Gulf of Finland is no more than 20-25 km away, but it cannot be seen from here as well.
13. Another trench in the bedrock.
14. This one actually ends in a door leading to one of the bunkers! I didn't do much research about the museum in advance, and I assumed the bunkers themselves are not actually open to public. It turned out they are. I think there are three accessible bunkers, open, lit and furnished, and also a few abandoned ones, dark and visited at one's own risk. Only one bunker is usually locked and open only for guided tours.
15. Going inside.
16. Thick inner blast door.
17. This small bunker is converted into an exhibition of weapons commonly used by the Finnish infantry.
18. This for example is the standard submachine gun of Finnish forces, named simply Suomi (also Suomi KP/-31). Its variant for bunker installation is visible below. Suomi along with many other Finnish firearms was designed by Aimo Lahti, who was sort of the Finnish counterpart to Kalashnikov.
19. Yet another trench, and this one leads us to...
20. Another bunker! Notice also wooden reinforcements of the dirt part of the trench.
21. Wow, this one is quite deep underground.
22. Another blast door.
23. The door features a ridiculously simple and ingenious trick for the defense. Supposing you're trapped in this bunker, and the enemy troops already descend down the stairway with guns drawn. In this case, you just lock the door, wait until they're on the other side on the door, and put a grenade into this hole. The grenade rolls down a narrow tube right under their feet, and boom! All you have to do is scrub their remains off. I was very impressed with this invention. I would have never thought of anything like this.
24. This bunker holds a 45 mm anti-tank gun. It seemed we descended fairly deep underground, but we're actually inside a huge above-ground rock, and this gun sticks out of its side. The designation M 40 is a little odd; it took a bit of Googling to figure out that it actually refers to a trophy Soviet gun, a 1932 design. You can look through the eyepiece and even try to aim the gun.
25. A ladder to a watch dome. The sign says that the thickness of the concrete above is 2.1 m, with a further 1.5-3 m or rock on top! This thing must be able to take a nuclear bomb hit! Also notice the anti-tank gun shell.
26. Down one more trench we go.
27. And into one more bunker.
28. This one is the largest of the three, intended to house 20 troops. It is relatively self-sufficient; for example, here's its toilet.
29. The bunker can defend itself with a machine gun with a water-cooled barrel.
30. Additionally there is a long and very narrow hole from which the defenders could shoot with their firearms (in the extreme foreground to the left).
31. It is really very narrow.
32. The bunks, looking appropriately spartan.
33. This odd contraption is apparently the air conditioning machine. Was it really hand operated?
34. The stove looks more like what you'd expect. In an alcove behind the stove, not visible here, is a water well.
35. This huge excavation is where another bunker was supposed to be built. It gives you an idea of the size of these structures. And remember that there were over seven hundred of them.
36. An anti-tank ditch.
37. A simple machine gun post.
38. One of the abandoned bunkers (or more precisely one of the bunkers which were never restored). There are two abandoned bunkers around here; one of them is simply empty and dark, and another is actually flooded. The signs warn that the latter one is very dangerous to explore due to danger of slipping on the flooded floor and falling into the submerged water well.
39. Rows of dragon's teeth along a gravel road.
42. There are both rock and concrete dragon's teeth in assortment.
43. In the place whether dragon's teeth cross the Road 384 there are two stone blocks with yellow "retarded lion" of Finland carved on them.
44. There is a tank, although I'm not sure if it is actually in any way relevant to the Salpa Line. It is an ordinary Soviet T-34-85, moreover, according to name plates, it was actually built after war in Czechoslovakia, in 1951.
45. I read later that it is actually possibly to climb inside the tank, but I didn't realize this at the time. A motorbike of some Finnish guy is visible next to the tank; a group of them drove up to the museum shortly after me.
46. The rocky hill near the modern Road 384. Can you notice the small rectangular hole in the rock face to the right? That's where the "M 40" anti tank gun from one of the previously seen bunkers sticks out from.
47. Just some random Finnish guy happily driving a tractor along Road 384. The road continues on to Taavetti, if you wonder; that's a small town between Kouvola and Lappeenranta.
48. Another anti-tank gun, it is not hidden into any bunker.
49. But look how conveniently it is placed! A long anti-tank ditch is dug in the forest, and the gun points right down that ditch to finish off any stuck tank.
50. Well, and that will be all for today; I'm driving back on Road 384 towards Virolahti. There are some exhibits I missed but there aren't many of them.
Some final notes if you got interested in seeing more of the Salpa Line. There is another museum, Bunkkerimuseo fairly close by in Virolahti. I'm not sure how its exhibition differs from the Salpa Line Museum.
The southernmost section of the Salpa Line (between Virolahti and Luumäki) is generally the best fortified one, as it was expected that the main Soviet assault would come here. A large part of this section can be visited on foot. There is a hiking trail, named Salpapolku, which starts in Majaniemi at the cost of the Gulf of Finland in Virolahti, and ends in Hostikka in a few kilometers from Ylämaa. The trail is 55 km long, a multiple day hike, but it should still be a pleasant enough walk. It passes through both Salpa Line Museum and Bunkkerimuseo. There are laavus (lean-tos) and more exquisite accomodation along the trail. Unfortunately both trailheads utterly lack any public transport, so you'll have to either return back the same way, or take a (very expensive) taxi. Cycling is also an option I believe. Here's an excellent information page about Salpapolku trail, in particular featuring a PDF brochure with a detailed topographic map.
There are many more Salpa Line fortifications in other parts of Finland as well. This seems to be a fairly complete guide covering everything up to Southern Lapland, although the Flash website looks dated ("Greater Salpa", "Salpa of islands and lakes" and "Salpa of wilderness" are the sections you need).
That's all, and for the next post we'll go into Hamina, a charming octagon of a town.