In internet arguments and popular culture, it is frequently claimed that the stridsvagn 103 (strv 103, “S-tank”) was a defensive tank, or basically a modern tank destroyer. It was, claims the common wisdom (perpetrated and repeated in media such as History Channel), meant to dig down in a forest, take a few shots at attacking Soviet tanks and then retreat, using its rear driver to its advantage. In the recently revealed Swedish tree for World of Tanks, it is indeed classified as a tank destroyer – mainly for game mechanics reasons, though, not because of a misunderstanding of its role. Even in the Swedish army, some officers (mainly ones who had no experience on the tank) thought it was worthless for traditional tank work – that is, offensive tasks. In this essay, I will show that this is simply not true: the Swedish army set out to figure out how to build a good tank, came up with the S-tank idea, developed and built that idea as a tank, which it then proceeded to use operationally as a tank.

The origins of the strv 103, or “alternative S”

In 1957, the Swedish army initiated a study of the future of warfare, in order to determine what weapons technology it should pursue during the 1960’s – as well as many other things. One of the sub-committees of this study was tasked with studying direct-fire infantry support weapon systems, such as tanks, anti-tank weapons, direct-fire crew-served weapons, etc. The central question that the sub-committee was tasked with answering was: “How should our system for direct fire (both anti-tank and anti-personnel fire) work around 1970 and in the time immediately thereafter?” 1

Additionally, the committee was asked four more specific questions, two of which had to do with tanks. First, it was asked to draw up technical requirements for a new tank to be in service around 1965, and while doing so investigate the appropriate trade-off between firepower, speed and protection – perhaps more than one type of tank would be needed? Second, it was asked to study how tanks were to be integrated into the army organization, keeping in mind the requirement to be able to quickly concentrate strong tank formations that would allow attacking strategically important locations such as a hostile beachhead, and in connection to this recommend a minimum number of tanks required in the entire army. Here, it is already becoming apparent what the army was thinking about tanks.

As a part of its work, the committee naturally kept tabs on foreign design trends. It appeared that there were two main schools of tank design thought in the West: one Anglo-American and one French-German one. The Brits and the Americans, the committee found, were intending to develop heavier tanks with more armor, perhaps around 45 tons – this trend would eventually materialize as the Chieftain and the M60. The Germans and the French on the other hand were aiming at lighter and faster tanks, around 30 tons, which would eventually materialize as the Leopard I and the AMX-30. The latter school thought that it would be impossible to combine decent mobility with enough armor to protect against the constantly improving HEAT rounds of the period, so they simply didn’t bother with much armor. For comparison purposes, these hypothetical tanks were designated the “A-tank” and the “T-tank” respectively, where A stood for America and T for Tyskland (the Swedish word for Germany). Additionally, the committee also studied a newly invented Swedish concept which had been patented in 1956 by an engineer at the Army Ordnance Administration (Kungl. Armétygförvaltningen), Sven Berge – consistently enough, it was named the “S-tank”. The S-tank concept lacked a turret and had a two-man or possibly even one-man crew, and because of this it could be designed with extremely well sloped front armor which would protect against the kinetic armor-piercing rounds of the period. The turretless design also allowed for a standoff screen in the front of the tank for protection against HEAT rounds. In short, it could potentially offer the protection of the A-tank with the same low weight and high power-to-weight ratio as the T-tank. Low weight was considered very important for strategic mobility reasons – with a lighter tank, it was easier to find railroad cars that could transport it and bridges that could support its weight.

After conducting a number of sub-studies (on things like the probability of victory in hypothetical duels between the three alternatives above, the effects of nuclear radiation on tank crews, the development of IR night vision devices, and war games involving tank assaults into beachheads) the committee delivered its report in May 1958. In regards to tanks, it recommended that development should be a started on a well armored tank much like the A-tank, and that development in the UK and the US should be monitored and the possibility of buying a design from either country be kept open. However, the committee also found that “alternative S” was interesting enough to merit further study, and recommended that some feasibility trials be conducted, at a limited scale. Furthermore the committee also found that newer, better tanks that were capable of fighting modern tanks tanks head on should be organized into armored brigades capable of attacking an opponent in open terrain, while older tanks should be assigned to direct infantry support only, in anti-tank companies in the infantry brigades.

It is already apparent where we’re heading: the army concluded that it needed a modern tank for its armored brigades, and the role of the armored brigades was an offensive one – counterattacking a beachhead being the typical example of an operation such a brigade might carry out. The S-tank was conceived as an offensive weapon, considered equal in role and performance to the foreign tanks then in development.

The development process

As the committee recommended, so were it to be, and initial work on some S-tank test rigs was contracted to Bofors in 1958. The development at this early stage was focused on a 30-ton two-man tank with a conventionally elevating gun, fed by an autoloader using two-piece ammunition (the “A-tank” proposal that was under development at the same time was to use the same gun and ammunition). By March 1959, however, the army had changed its mind, for several reasons. Experiments with two-man crews in other armored vehicles at the Armored Forces School (Pansartruppskolan) had found that just driving, spotting and firing was so taxing on the crew that it left no mental resources over to manage communication with the rest of the unit, especially not if the commander also had to handle a secondary weapon, such as a machine gun or an autocannon. Consulting German war veterans at the West German armor school in Munster about their experiences pointed in the same direction: two men simply weren’t enough, especially not with the complex radio equipment in use in the late 50’s. Autoloaders were not entirely trusted either; it seemed like it would be a good idea to have someone who could monitor it and fix potential jams. A third crew member was necessary, and finding space for him would increase the weight of the tank. However, it seemed that this could be solved by returning to Sven Berge’s original gun elevation idea, more or less as envisioned in his 1956 patent. By fixing the gun in the chassis in the vertical axis too and instead elevating by moving the road wheels, the autoloader mechanism could be moved to the rear of the tank, where the would also be room for the third man. Early on in the development, the idea to give the driver/gunner a fully rotating seat and a set of rear-facing controls had been floated around with the intention of improving tactical flexibility – reversing in a tank is ordinarily quite difficult and usually involves a guide on the outside of the vehicle since the driver has zero visibility to the rear – but with a third man in the tank, it was natural to give him the rear controls instead, and thus the rear driver/radioman was in place.

The various trials were mainly positive – the concept was found to be workable in practice, and the A-tank development was put on hold. A prototype series of 10 S-tanks was ordered in 1960 – the positives seemed to by far outweigh the negatives already at this point, but further studies were conducted. In 1961, the Armored Forces School investigated the possible downsides of a lack of gun stabilization and an inability to engage targets that were not directly in front of the tank. The study stated that at the time, even in tanks with stabilization, firing on the move at distances greater than 500 meters was mostly a waste of ammunition. Even at shorter ranges only big targets (i.e. tanks) were to be fired at on the move. According to the study, the main benefit of stabilization was taking 2-3 seconds off of the time between stopping and opening fire. With this in mind, as well as the fact that in the S-tank it would be possible for the commander to take over control and show the gunner/driver a spotted target, it is easy to see why the study concluded that it could not see why the S-tank would be inferior in reaction time to a turreted tank. The ability to easily and quickly retreat with the front armor towards the enemy (thanks to the rear driver) was also considered an advantage. 3

By 1961, the army HQ was calling for at least 200 new tanks, preferably with deliveries starting in 1965. The debate regarding which tank to buy would continue into 1962 – the S-tank was compared to both other Western tanks of the time and estimates of the Soviet adversary tanks in a number of simulations and paper wargames. The conclusion was that while the Chieftain was good, the S-tank was better – it was estimated to have very similar protection but was much lighter and presented a smaller target area and a lower silhouette. 4

As demonstrated above, the strv 103 was developed with the same kind of requirements as a turreted tank. It should hopefully not come as a surprise that when it was taken into service in the armored brigades, it filled the exact same role as a turreted tank. In the 1970’s, the Swedish army’s modern tanks (the strv 103 and the Centurion) were organized in seven armored brigades, plus a few independent mechanized battalions. Each armored brigade had 72 tanks, 72 infantry squads in APC’s and a lot of supporting assets (AA, artillery, recon, logistics etc). There were dozens of infantry brigades, but the few armored brigades were the army’s spearhead and the only Swedish army formation that could really conduct an offensive operation in depth against a mechanized enemy. If you take a look at a map, you might be wondering where the Swedish army imagined it was going to conduct a mechanized offensive – while most of the country was east of the Iron Curtain, it was entirely surrounded by water and friendly countries, and the army had no landing craft capable of crossing the Baltic sea. Of course, the answer is the one that was hinted at above: the armored brigades were for counter-attacking beachheads, airborne landings or, if it came to that, an enemy that had established a foothold in the country. The infantry brigades were well suited to defending and delaying, but since they didn’t have any form of armored transportation they were only really capable of attacking in what was termed “covered terrain” (i.e. mostly forests and urban areas). Open country was tank country, and consequently the armored brigades had their initial positions in strategically important open areas. Three of the seven armored brigades had their initial positions in the provinces of Skåne and Blekinge, at the very southern tip of the country – mostly flat and open terrain, and only a few hours from East Germany and Poland by ship. One was stationed on the island of Gotland (also flat and open terrain, and not a big island at all), two in the densely populated and strategically important Stockholm and lake Mälaren area (one in Strängnäs, south of the lake, and one in Enköping, north of the lake) and finally one in Skövde on the big plains in the southwestern part of the country where a lot of important air force bases were located – it was also intended as strategic reserve and could easily be transported to several important parts of the country. In the 1970’s, two of the brigades in Skåne and the one in Skövde were equipped with strv 103’s; the rest had Centurions. Strategically, it didn’t matter which tank the brigade had – it was expected to fill the same role and had almost exactly the same organization and equipment (other than the tanks themselves). 5

Tactically, there were a few differences between strv 103’s and Centurions, but they weren’t huge. The Swedish tank gunnery doctrine was developed with the expectation of encountering an enemy with far more tanks and other AFV’s than the Swedes could expect to have, and because of this, it heavily emphasized well-aimed fire. In the 1974 field manual for tank platoons (same for both Centurions and strv 103’s – only the manual for individual tank crews differed), the important points were summarized as follows.

When firing against tanks and other armored vehicles, surprising the enemy when opening fire and achieving local superiority when it comes to firepower are both very important. Strive for quick and well-aimed fire and to present the smallest possible target to the enemy. 6

The 1979 tank gunnery field manual agreed, and stated in underlined lettering:

In a tank vs tank duel, the tank that fires *first* will destroy its opponent in four duels out of five.

The tank that gets the *first* hit in is four times more likely to win the duel.

The goal to strive for with all tank gun fire is to both hit with the first round and to destroy the target with the first hit.

A well-trained tank crew shall be able to hit with the first round and destroy their target within ten seconds of first opening fire. 7

The manuals had some rules of thumb regarding when not to take a shot. A single stationary tank with no particular fire mission should not take shots at a tank front-sized target beyond 1300 meters, a stationary tank turret-sized target beyond 1000 meters or a moving tank side-size target at beyond 800 meters – beyond these distances, the manual explained, first round hit probability fell below 50% and that made the shot not worth taking. If a rangefinder was available to reduce the risk of misjudging the elevation, these distances could be extended to 2000, 1500 and 1000 meters respectively, but at longer ranges it was better to fire by platoon. Focusing fire was generally encouraged. Naturally, the manual also discouraged firing on the move, even in a tank with gun stabilization like the Centurion. In a Centurion, firing on the move was permitted at distances up to 800 meters, and it was only to be done if there was a very good reason for doing it – for example, returning fire on a tank that had open fire on your own tank, or attempting to suppress a AT gun or ATGM crew that had just fired. In the strv 103, firing on the move was only permitted at distances up to 200 meters, which is basically knife fighting range in a tank.

In both the strv 103 and the Centurion, the field manuals encouraged advancing by leapfrog – one platoon (or individual tank) provided stationary fire support while another advances to a good position, then the rear platoon advances past that to the next good position and so on. Both on the offense and on the defense, choosing good positions (i.e. hull down if possible) to stop and fire from was strongly encouraged.

In light of the above, it should not be hard to see that the strv 103’s inability to fire on the move was not considered a significant disadvantage – it fit well into the Swedish doctrine.

Conclusion

The stridsvagn 103 was conceived as a tank, developed in response to a demand for a tank, and used as a tank. It was not a tank destroyer or a “defensive” vehicle. Repeated trials both in Sweden and abroad showed that in most cases it was insignificantly slower to react to a target appearing on its side than a turreted tank was. In fact, due to its duplicated controls (the commander could override the gunner/driver’s controls and, for example, point the tank at a target that he could see through his rotating cupola but the gunner/driver hadn’t spotted) it could even be faster to react than a turreted tank without similar functionality – the turreted tank’s commander would have to talk the gunner into finding the target. The inability to fire on the move was not considered a significant disadvantage considering the Swedish gunnery doctrine at the time.

The strv 103 proved to be an evolutionary dead end, however. Stabilization technology improved rapidly during the 1970’s, especially with the introduction of gun-follows-sight technology, and the next generation of Western MBT’s that appeared around 1980 were only slightly less accurate on the move than they were at a standstill. The strv 103’s heavily sloped but not all that thick front armor which offered good protection against 1960’s armor-piercing rounds was also completely insufficient against newer 1970’s “long rod” penetrators. It was a very innovative and very Swedish think-outside-the-box solution in 1960, but it should have been replaced or at least relegated to a less demanding role around 1980-1985 – indeed, the original requirements had called for a technical lifetime of 15 years.

Footnotes