Inner Border: 1

 Inner German border (German; Innerdeutsche Grenze, French: Frontière interallemande, Russian: Государственная граница ГДР и ФРГ)

The Inner German border (German: Innerdeutsche Grenze pronounced or Deutsch-deutsche Grenze pronounced]; initially also Zonengrenze pronounced was the border between the German Democratic Republic (GDR, East Germany) and the Federal Republic of Germany (FRG, West Germany) from 1949 to 1990. Not including the similar and physically separate Berlin Wall, the border was 1,393 kilometres (866 mi) long and ran from the Baltic Sea to Czechoslovakia.  It was formally established on 1 July 1945 as the boundary between the Western and Soviet occupation zones of former Nazi Germany. On the eastern side, it was made one of the world's most heavily fortified frontiers, defined by a continuous line of high metal fences and walls, barbed wire, alarms, anti-vehicle ditches, watchtowers, automatic booby traps, and minefields. It was patrolled by 50,000 armed East German guards who faced tens of thousands of West German, British, and US guards and soldiers.  In the hinterlands behind the border were more than a million North Atlantic Treaty Organisation (NATO) and Warsaw Pact troops.  The border was a physical manifestation of Sir Winston Churchill's metaphorical Iron Curtain that separated the Soviet and Western blocs during the Cold War. It marked the boundary between two economic systems—capitalism and socialism. Built by East Germany in phases from 1952 to the late 1980s,  the fortifications were constructed to stop the large-scale emigration of East German citizens to the West, about 1,000 of whom are said to have died trying to cross it during its 45-year existence.  It caused widespread economic and social disruption on both sides; East Germans living in the region suffered especially draconian restrictions. The better-known Berlin Wall was a physically separate, less elaborate, and much shorter border barrier surrounding West Berlin, more than 155 kilometres (96 mi) to the east of the inner German border. Berlin, which was entirely within the Soviet zone, had been similarly divided by the four powers after World War II, thus creating an exclave surrounded by East Germany that was closely aligned with (but not formally part of) West Germany.  On 9 November 1989, the East German government announced the opening of the Berlin Wall and the inner German border. Over the following days, millions of East Germans poured into the West to visit. Hundreds of thousands moved permanently to the West in the following months as more crossings were opened, and ties between long-divided communities were re-established as border controls became little more than a cursory formality. The inner German border was not completely abandoned until 1 July 1990, exactly 45 years to the day since its establishment, and only three months before German reunification formally ended Germany's division.  Little remains of the inner German border's fortifications. Its route has been declared part of the European Green Belt linking national parks and nature reserves along the course of the old Iron Curtain from the Arctic Circle to the Black Sea. Several museums and memorials along the old border commemorate the division and reunification of Germany and, in some places, preserve elements of the fortifications. 

Origins:

(Post-Nazi German occupation borders and territories from 1945 to 1949. British (green), French (blue), American (orange) and Soviet (red) occupation zones. Saar Protectorate (light blue) in the west under the control of France. Berlin is the quadripartite area shown within the red Soviet zone. Bremen consists of the two orange American exclaves in the British sector.)

 The Allied zones of occupation in Germany, highlighting the inner German border (heavy black line), the originally Soviet-occupied zone (red) and the area from which US/UK troops withdrew in July 1945 (purple). The provincial boundaries are those of Nazi Germany, before the modern federal states were established. The inner German border originated from plans by the Allies of World War II to divide a defeated Germany into occupation zones. Their boundaries were drawn along the territorial boundaries of 19th-century German states and provinces that had largely disappeared with the unification of Germany in 1871.[8] Three zones were agreed on, each covering roughly a third of Germany: a British zone in the north-west, an American zone in the south and a Soviet zone in the East. France was later given a zone in the southwest of Germany, neighbouring with France, carved out of the British and American zones.  The division of Germany was put into effect on 1 July 1945. Because of their unexpectedly rapid advances through central Germany in the final weeks of the war, British and American troops occupied large areas that had been assigned to the Soviet zone of occupation. The redeployment of Western troops prompted many Germans to flee to the West to escape the Soviet takeover of the remainder of the Soviet zone.  The wartime Allies initially worked together under the auspices of the Allied Control Council (ACC) for Germany.  Cooperation between the Western Allies and the Soviets ultimately broke down because of disagreements over Germany's political and economic future. In May 1949, the three western occupation zones were merged to form the Federal Republic of Germany (FRG) with a freely elected government. In October, the Soviet zone was proclaimed the German Democratic Republic (GDR), under communist rule.  From the outset, West Germany and the Allies rejected East Germany's legitimacy.  The creation of East Germany was deemed a communist/Soviet fait accompli, without a freely or fairly elected government. The FRG regarded German citizenship and rights as applying equally to West and East German citizens. An East German who escaped or was released to the West was automatically granted West German rights including residence, the right to work, and (later) EEC freedom of movement; West German laws were deemed to be applicable in the East. East Germans thus had a powerful incentive to move to the West, where they would enjoy greater freedom and economic prospects. The East German government sought to define the country as a legitimate state in its own right  and portrayed West Germany as enemy territory (feindliches Ausland) – a capitalist, semi-fascist state that exploited its citizens, sought to regain the lost territories of the Third Reich, and stood opposed to the peaceful socialism of the GDR.

1945–1952: the "Green Border":

In the early days of the occupation, the Allies controlled traffic between the zones to manage the flow of refugees and prevent the escape of former Nazi officials and intelligence officers. These controls were gradually lifted in the Western zones, but were tightened between Western and Soviet zones in 1946 to stem a flow of economic and political refugees from the Soviet zone. Between October 1945 and June 1946, 1.6 million Germans left the Soviet zone for the west.  The east–west interzonal border became steadily more tense as the relationship between the Western Allies and the Soviets deteriorated.  From September 1947, an increasingly strict regime was imposed on the eastern Soviet zone boundary. The number of Soviet soldiers on the boundary was increased and supplemented with border guards from the newly established East German Volkspolizei ("People's Police"). Many unofficial crossing points were blocked with ditches and barricades.  The West Germans also stepped up security with the establishment in 1952 of the Federal Border Protection force of 20,000 men – the Bundesgrenzschutz, or BGS; however, Allied troops (the British in the north, the Americans in the south) retained responsibility for the military security of the border.  The boundary line was nonetheless still fairly easy to cross. Local inhabitants were able to maintain fields on the other side, or even to live on one side and work on the other. Refugees were able to sneak across or bribe the guards, and the smuggling of goods in both directions was rife. The flow of emigrants remained large despite the increase in East German security measures: 675,000 people fled to West Germany between 1949 and 1952. 

1952–1967: the "special regime":

The relative openness of the border ended abruptly on 26 May 1952, when East Germany implemented a "special regime on the demarcation line", justified as a measure to keep out "spies, diversionists, terrorists and smugglers". The East German move was taken to limit the continuing exodus of its citizens, which threatened the viability of East Germany's economy.  A ploughed strip 10 m (32.8 ft) wide was created along the entire length of the inner German border. An adjoining "protective strip" (Schutzstreifen) 500 m (1,640 ft) wide was placed under tight control. A "restricted zone" (Sperrzone) a further 5 km (3.1 mi) wide was created in which only those holding a special permit could live or work. Trees and brush were cut down along the border to clear lines of sight for the guards and to eliminate cover for would-be crossers. Houses adjoining the border were torn down, bridges were closed, and barbed-wire fencing was put up in many places. Farmers were permitted to work their fields along the border only in daylight hours and under the watch of armed guards, who were authorised to use weapons if their orders were not obeyed. Border communities on both sides suffered acute disruption. Farms, coal mines, and even houses were split in two by the sudden closure of the border.  More than 8,300 East German civilians living along the border were forcibly resettled in a programme codenamed "Operation Vermin" (Aktion Ungeziefer). Another 3,000 residents, realising that they were about to be expelled from their homes, fled to the West. The seal around the country was expanded in July 1962, when East Germany declared its entire Baltic coast a border zone subject to closures and restrictions. The border between East and West Berlin was also significantly tightened, although not fully closed; East Germans were still able to cross into West Berlin, which then became the main route by which East Germans migrated to the West.  Between 1949 and the building of the Berlin Wall in 1961, an estimated 3.5 million East Germans – a sixth of the entire population – emigrated to the West, most via Berlin.  The railways between East Berlin and other important parts of East Germany went through West Berlin, so an easy way of going to West Berlin was leaving such a train. This railway configuration could not easily be changed, but a new 125 km (78 mi) long railway was built around West Berlin. Following the completion of the Berlin outer ring in 1961, sealing off the East German border with West Berlin became more feasible, and ultimately became a reality in August of that year. 

1967–1989: the "modern frontier":

(Third Generation Inner German Border Wall Diagram - 1984)

East Germany decided to upgrade the fortifications in the late 1960s to establish a "modern frontier" that would be far more difficult to cross. Barbed-wire fences were replaced with harder-to-climb expanded metal barriers; directional anti-personnel mines and anti-vehicle ditches blocked the movement of people and vehicles; tripwires and electric signals helped guards to detect escapees; all-weather patrol roads enabled rapid access to any point along the border; and wooden guard towers were replaced with prefabricated concrete towers and observation bunkers.  Construction of the new border system started in September 1967. Nearly 1,300 kilometres (808 mi) of new fencing was built, usually further back from the geographical line than the old barbed-wire fences. The upgrade programme continued well into the 1980s. The new system immediately reduced the number of successful escapes from around 1,000 people a year in the mid-1960s to only about 120 per year a decade later. The introduction of West German Chancellor Willy Brandt's Ostpolitik ("Eastern Policy") at the end of the 1960s reduced tensions between the two German states. It led to a series of treaties and agreements in the early 1970s, most significantly a treaty in which East and West Germany recognised each other's sovereignty and supported each other's applications for UN membership, although East Germans leaving for the West retained the right to claim a West German passport.  Reunification remained a theoretical objective for West Germany, but in practice that objective was put aside by the West and abandoned entirely by the East.  New crossing points were established and East German crossing regulations were slightly relaxed, although the fortifications were as rigorously maintained as ever. In 1988, the East German leadership considered proposals to replace the expensive and intrusive fortifications with a high-technology system codenamed Grenze 2000. Drawing on technology used by the Soviet Army during the Soviet–Afghan War, it would have replaced the fences with sensors and detectors. However, the plan was never implemented.

Economic and social impact:

The closure of the border had a substantial economic and social impact on both halves of Germany. Cross-border transport links were largely severed; 10 main railway lines, 24 secondary lines, 23 autobahns or national roads, 140 regional roads and thousands of smaller roads, paths and waterways were blocked or otherwise interrupted. The tightest level of closure came in 1966, by which time only six railway lines, three autobahns, one regional road and two waterways were left open. When relations between the two states eased in the 1970s, the GDR agreed to open more crossing points in exchange for economic assistance. Telephone and mail communications operated throughout the Cold War, although packages and letters were routinely opened and telephone calls were monitored by the East German secret police.  The economic impact of the border was harsh. Many towns and villages were severed from their markets and economic hinterlands, which caused areas close to the border to go into an economic and demographic decline. The two German states responded to the problem in different ways. West Germany gave substantial subsidies to communities under the "Aid to border regions" programme, an initiative begun in 1971 to save them from total decline. Infrastructure and businesses along the border benefited from substantial state investment. East Germany's communities had a much harder time, because the country was poorer and their government imposed severe restrictions on them. The border region was progressively depopulated through the clearance of numerous villages and the forced relocation of their inhabitants. Border towns suffered draconian building restrictions: inhabitants were forbidden from building new houses and even repairing existing buildings, causing infrastructure to fall into severe decay.  The state did little but to provide a 15% income supplement to those living in the Sperrzone and Schutzstreifen; but this did not halt the shrinkage of the border population, as younger people moved elsewhere to find employment and better living conditions. The GDR bore a huge economic cost for its creation of the border zone and the building and maintenance of its fortifications. The zone consumed around 6,900 square kilometres (2,700 sq mi) – more than six per cent of the East's territory,  within which economic activity was severely curtailed or ceased entirely. The actual cost of the border system was a closely guarded secret, and even today it is uncertain exactly how much it cost to build and maintain. The BT-9 watchtowers each cost around 65,000 East German marks to build and the expanded metal fences cost around 151,800 marks per kilometre. The implementation of the "modern frontier" in the 1970s led to a major increase in personnel costs. The total annual expenditure on GDR border troops rose from 600 million marks per annum in 1970 to nearly 1 billion by 1983. In early 1989, East German economists calculated that each arrest cost the equivalent of 2.1 million marks, three times the average value to the state of each working person. 

Tourism:

The Berlin Wall was a specific piece of the Inner Border that became the physical embodiment of the Iron Curtain that stood between East Germany and West Germany in the decades following the conclusion of World War II. The Berlin Wall stretched approximately 28 miles (45 km) through the city of Berlin and another 75 miles (120 km) around the edges of West Berlin, and stood close to 15 feet (5 meters) in height.  The sheer physical stature of the Berlin Wall in addition to becoming an iconic, international symbol of the Cold War and its virtues, drove it to become a popular site of tourism throughout its existence, and even after its dismantling. Tourism of the Berlin Wall reached its height in 1961, although an exact number cannot be given for the number of visitors to the Berlin Wall, as there were no official records of tourism to the site made at the time. Estimates, however, are provided through the counting of tourists by Western and Eastern border guards. The numbers obtained from the border guards suggest that Berlin Wall tourism was a popular outing for German people and foreigners alike, it is reported that the Berlin Wall received approximately 1.65 million tourists in 1969 alone, with around 23,000 of those being foreign visitors.  Day trips were the most popular of the ways to visit the Berlin Wall, which could be conducted even through organized tours that were governmentally funded, so long as they were presented as educational in nature. 

Views of the border:

The two German governments promoted very different views of the border. The GDR saw it as the international frontier of a sovereign state – a defensive rampart against Western aggression.  In Grenzer ("Border Guard"), a 1981 East German Army propaganda film, NATO and West German troops and tanks were depicted as ruthless militarists advancing towards East Germany. Border troops interviewed in the film described what they saw as the rightfulness of their cause and the threat of Western agents, spies and provocateurs. Their colleagues killed on the border were hailed as heroes and schoolchildren in East Berlin were depicted saluting their memorial.  However, West German propaganda leaflets referred to the border as merely "the demarcation line of the Soviet occupation zone", and emphasised the cruelty and injustice of the division of Germany.  Signs along the Western side of the frontier declared "Hier ist Deutschland nicht zu Ende – Auch drüben ist Vaterland!" ("Germany does not end here: the Fatherland is over there too!") Whereas East Germany kept its civilians well away from the border, West Germany actively encouraged tourism, and locations where the border was especially intrusive became tourist attractions. One example was the divided village of Mödlareuth in Bavaria. The Associated Press reported in 1976 that "Western tourists by the busload come out to have their pictures taken against the backdrop of the latest Communist walled city [and] the concrete blockhouse and the bunker-slits protruding from the green hillock where a collective's cows were grazing." At Zimmerau, in Bavaria, a 38-metre (125 ft) observation tower (the Bayernturm) was constructed in 1966 to give visitors a view across the hills into East Germany.  The inhabitants of the East German village of Kella found themselves becoming a tourist attraction for Westerners in the 1970s and 1980s. A viewing point, the "Window on Kella", was established on a nearby hilltop from which tourists could peer across the border with binoculars and telescopes.  To the amusement of many, a nudist beach was opened on the Western side in 1975 immediately adjoining the border's terminus near the Baltic Sea port of Travemünde. Visitors often sought to have a nude photograph taken below a looming East German watchtower; the West Germans noted "a lot more movement on that watchtower since the nudist beach opened".

Restricted zone:

A person attempting to make an illegal crossing of the inner German border around 1980, travelling from east to west, would first come to the "restricted zone" (Sperrzone). This was a 5 kilometres (3.1 mi) wide area running parallel to the border to which access was heavily restricted. Its inhabitants could only enter and leave using special permits, were not permitted to enter other villages within the zone, and were subjected to night time curfews.[43][56][57] It was not fenced off, but access roads were blocked by checkpoints. On the far side of the Sperrzone was the signal fence (Signalzaun), a continuous expanded metal fence 1,185 kilometres (736 mi) long and 2 metres (6.6 ft) high. The fence was lined with low-voltage electrified strands of barbed wire. When the wire was touched or cut, an alarm was activated to alert nearby guards. 

Protective strip:

On the other side of the signal fence lay the heavily guarded "protective strip" (Schutzstreifen), 500 to 1,000 metres (1,600 to 3,300 ft) wide, which adjoined the border itself.  It was monitored by guards stationed in concrete, steel and wooden watchtowers constructed at regular intervals along the entire length of the border. Nearly 700 such watchtowers had been built by 1989;[59] each of the larger ones was equipped with a powerful 1,000-watt rotating searchlight (Suchscheinwerfer) and firing ports to enable the guards to open fire without having to go outside. Their entrances were always positioned facing towards the East German side, so that observers in the West could not see guards going in or out. Around 1,000 two-man observation bunkers also stood along the length of the border.  The guards used an all-weather patrol road (Kolonnenweg, literally "column way") to patrol the border and travel rapidly to the scene of an attempted crossing. It consisted of two parallel lines of perforated concrete blocks that ran beside the border for around 900 kilometres (560 mi). Next to the Kolonnenweg was one of the control strips (Kontrollstreifen), a line of bare earth running parallel to the fences along almost the entire length of the border. There were two control strips, both located on the inward-facing sides of the fences. The secondary "K2" strip, 2 metres (6.6 ft) wide, ran alongside the signal fence, while the primary "K6" strip, 6 metres (20 ft) wide, ran along the inside of the fence or wall. In places where the border was vulnerable to escape attempts, the control strip was illuminated at night by high-intensity floodlights (Beleuchtungsanlage), which were also used at points where rivers and streams crossed the border. Anyone attempting to cross the control strips would leave footprints, which were quickly detected by patrols. This enabled the guards to identify otherwise undetected escape attempts, recording how many individuals had crossed, where escape attempts were being made and at which times of day escapees were active. From this information, the guards were able to determine where and when patrols needed to be increased, where improved surveillance from watchtowers and bunkers was required, and which areas needed additional fortifications. Anti-vehicle barriers were installed on the other side of the primary control strip. In some locations, Czech hedgehog barricades, known in German as Panzersperre or Stahligel ("steel hedgehogs"), were used to prevent vehicles being used to cross the border. Elsewhere, V-shaped anti-vehicle ditches known as Kraftfahrzeug-Sperrgraben (KFZ-Sperrgraben) were installed along 829 kilometres (515 mi) of the border and were absent only where natural obstacles such as streams, rivers, gullies or thick forests made such barriers unnecessary.

Outer fence, walls and minefields:

The outer fences were constructed in a number of phases, starting with the initial fortification of the border from May 1952. The first-generation fence was a crudely constructed single barbed-wire fence (Stacheldrahtzaun) which stood between 1.2 and 2.5 metres (3.9 and 8.2 ft) high and was built very close to the actual border line.  This was replaced in the late 1950s with parallel rows of more strongly constructed barbed-wire fences, sometimes with concertina wire placed between the fences as an additional obstacle. A "third-generation" fence, much more solidly constructed, was installed in an ongoing programme of improvements from the late 1960s to the 1980s. The fence line was moved back to create an outer strip between the fence and the actual border. The barbed-wire fences were replaced with a barrier that was usually 3.2–4.0 metres (10–13 ft) high. It was constructed with expanded metal mesh (Metallgitterzaun) panels. The openings in the mesh were generally too small to provide finger-holds and were very sharp. The panels could not easily be pulled down, as they overlapped, and they could not be cut through with a bolt- or wire-cutter. Nor could they be tunnelled under easily, as the bottom segment of the fences was partially buried in the ground. In a number of places, more lightly constructed fences (Lichtsperren) consisting of mesh and barbed wire lined the border.  The fences were not continuous and could be crossed at a number of places. Gates were installed to enable guards to patrol up to the line and to give engineers access for maintenance on the outward-facing side of the barrier.  In some places, villages adjoining the border were fenced with wooden board fences (Holzlattenzaun) or concrete barrier walls (Betonsperrmauern) standing around 3–4 metres (9.8–13.1 ft) high. Windows in buildings adjoining the border were bricked or boarded up, and buildings deemed too close to the border were pulled down. The barrier walls stood along only a small percentage of the border – 29.1 kilometres (18.1 mi) of the total length by 1989. Anti-personnel mines were installed along approximately half of the border's length starting in 1966; by the 1980s, some 1.3 million mines of various Soviet-made types had been laid.  In addition, from 1970 the outer fence was booby-trapped with around 60,000 SM-70 (Splittermine-70) directional anti-personnel mines. They were activated by tripwires connected to the firing mechanism. This detonated a horn-shaped charge filled with shrapnel that was sprayed in one direction along the line of the fence. The device was potentially lethal to a range of around 120 metres (390 ft). The mines were eventually removed by the end of 1984 in the face of international condemnation of the East German government.

Border line:

Until the late 1960s, the fortifications were constructed almost up to the actual border line. When the third-generation fortifications were constructed, the fences were moved back from between 20 metres (66 ft) to as much as 2 kilometres (1.2 mi). This gave the guards a clear field of fire to target escapees without shots landing in the West and provided a buffer zone where engineers could work on maintaining the outward face of the fence in East German territory. Access to the outer strip was very tightly controlled, to ensure that the guards themselves would not be tempted to escape. Although often described by Western sources as a "no-man's land", it was de jure wholly East German territory, and escapees could be arrested or shot. Westerners were prohibited from entering the area and thus could not go to the aid of escapees.  The actual line between West and East Germany was located on the far side of the outer strip. It was marked by granite stones (Grenzsteine) with the letters "DDR" carved on the west-facing edge. Around 2,600 distinctive East German concrete "barber pole" (Grenzsäule or Grenzpfähle) markers were installed just behind the border line at intervals of about 500 metres (1,600 ft). A metal coat of arms of East Germany (Staatsemblem) was fixed to the side of the marker facing West Germany.  On the West German side, there were no fortifications of any kind, nor even any patrol roads in most areas. Warning signs (Grenzschilder) with messages such as Achtung! Zonengrenze! ("Danger! Zonal border!") or Halt! Hier Zonengrenze ("Stop! Zonal border here") notified visitors. Foreign military personnel were restricted from approaching the border to avoid clashes or other unwanted incidents. Signs in English and German provided notifications of the distance to the border to prevent accidental crossings. No such restriction applied to Western civilians, who were free to go up to the border line, and there were no physical obstacles to stop their crossing it.

East Germany's sea border:

The inner German border system also extended along the Baltic coast, dubbed the "blue border" or sea border of the GDR. The coastline was partly fortified along the east side mouth of the river Trave opposite the West German port of Travemünde. Watchtowers, walls and fences stood along the marshy shoreline to deter escape attempts and the water was patrolled by high-speed East German boats. The continuous line of the inner German border ended at the peninsula of Priwall, still belonging to Travemünde, but already on the east side of the Trave. From there to Boltenhagen, along some 15 kilometres (9.3 mi) of the eastern shore of the Bay of Mecklenburg, the GDR shoreline was part of the restricted-access "protective strip" or Schutzgebiet. Security controls were imposed on the rest of the coast from Boltenhagen to Altwarp on the Polish border, including the whole of the islands of Poel, Rügen, Hiddensee, and Usedom as well as the peninsulas of Darß and Wustrow. The GDR implemented a variety of security measures along its Baltic coastline to hinder escape attempts. Camping and access to boats was severely limited[30] and 27 watchtowers were built along the Baltic coastline.  If a suspected escape attempt was spotted, high-speed patrol boats would be dispatched to intercept the fugitives. Armed patrols equipped with powerful mobile searchlights monitored the beaches. Escapees aimed for the western (West German) shore of the Bay of Mecklenburg, a Danish lightship off the port of Gedser, the southern Danish islands of Lolland and Falster, or simply the international shipping lanes in the hope of being picked up by a passing freighter. The Baltic Sea was, however, an extremely dangerous escape route. In all, 189 people are estimated to have died attempting to flee via the Baltic.  Some East Germans tried to escape by jumping overboard from East German ships docked in Baltic harbours. So many East Germans attempted to flee this way in Danish ports that harbourmasters installed extra life-saving equipment on quaysides where East German vessels docked. The GDR's government responded by stationing armed Transportpolizei (Trapos) on passenger ships to deal forcefully with escape attempts. On one occasion in August 1961, the Trapos caused an international incident in the Danish port of Gedser, when they beat up a would-be escapee on the quayside and opened fire, hitting a Danish boat in the harbour. The next day, thousands of Danes turned out to protest against "Vopo (Volkspolizei) methods". The "boat-jumpers" were eventually stopped by further restricting the already limited travel rights of the GDR's population.

River borders:

The border also ran along part of the length of three major rivers of central Germany: the Elbe between Lauenburg and Schnackenburg (around 95 km or 59 mi), the Werra and the Saale. The river borders were especially problematic; although the Western Allies and West Germany held that the demarcation line ran along the eastern bank, the East Germans and Soviets insisted that it was located in the middle of the river (the Thalweg principle). In practice, the waterways were shared equally but the navigation channels often strayed across the line. This led to tense confrontations as East or West German vessels sought to assert their right to free passage on the waterways. The rivers were as heavily guarded as other parts of the border. On the Elbe, East Germany maintained a fleet of about 30 fast patrol boats and West Germany had some 16 customs vessels. The river border was closely watched for escapees, many of whom drowned attempting to cross. Numerous bridges blown up in the closing days of the Second World War remained in ruins, while other surviving bridges were blocked or demolished on the East German side. There were no ferry crossings and river barges were rigorously inspected by the GDR border guards. To prevent escape attempts, the East German river banks were barricaded with a continuous line of metal fences and concrete walls. At one location, Rüterberg on the Elbe, the border fortifications completely surrounded the village and sealed off the inhabitants from the rest of East Germany as well as the West.

https://en.wikipedia.org/wiki/Inner_German_border