The territorial structure of the German Empire took shape in two stages: Firstly, in 1867, following Prussia’s victory in the German Confederation War and Austria’s withdrawal from German politics, 22 states north of the Main River united under Prussian leadership to form the North German Confederation (Constitution of 16 April 1867). Several German states were annexed by Prussia (Hanover, Hesse-Kassel, Nassau, the Free City of Frankfurt am Main). The former federal state of Luxembourg, together with the federal fortress located there, withdrew from the Confederation following a Prussian-French agreement and became fully sovereign. Later, following the joint victory over France, the southern German states of Bavaria, Württemberg and Baden (as well as Hesse-Darmstadt for its territories south of the Main) joined the North German Confederation in November 1870; this subsequently took the name ‘German Empire’ (the proclamation of the Emperor at the Palace of Versailles on 18 January 1871 was primarily of a symbolic nature). On 16 April 1871, the Empire adopted a new constitution. Its territory was expanded through the annexation of the provinces of Alsace and Lorraine, ceded by France under the Treaty of Frankfurt of 10 May 1871; these became the ‘Reichsland of Alsace-Lorraine’ and were not granted a constitution – and thus elevated to the status of a federal state – until 1911. Between 1871 and 1920 (when the Treaty of Versailles came into force), the territory of the German Empire covered 540,858 km². The overseas colonies, which were not part of the actual German territory, covered a total area of 2,658,450 km² in 1914.

As a result of the provisions of the Treaty of Versailles of 28 June 1919, Germany’s territory was reduced to 468,116 km² in 1920. The following territories were lost:

- Alsace-Lorraine (area 14,522 km²): The territory was placed under French administration without negotiation as early as the Armistice of 11 November 1918, but was not formally ceded until the Treaty of Versailles.

- Eupen-Malmedy, including Neutral-Moresnet (area 1,036 km²): This almost entirely German-speaking region was transferred to Belgium without a referendum as compensation for damage caused during the period of German occupation.

- North Schleswig (area 3,993 km²): This area (known as Zone I) was annexed to Denmark on 15 June 1920 following the referendum of 10 February 1920, whilst the southern Zone II remained part of Germany. The plebiscite was officially legitimised as the belated implementation of a provision of the 1866 Treaty of Vienna between Prussia and Austria. However, the Danish side was favoured by the fact that Zone I, where a clear decision in favour of Denmark was expected, was allocated in its entirety to the state chosen by the majority, whilst in the predominantly pro-German Zone II, the allocation was made on a district-by-district basis.

- The province of Posen, which had becomePrussian as a result of the partitions of Poland at the end of the 18th century , was ceded to Poland without a vote, with the exception of a few German-populated districts in the west and south; the ceded area amounted to 26,000 km².

- The majority of the former Prussian province of West Prussia, with the exception of Danzig/Gdańsk and the administrative district of Marienwerder/Kwidzyn – which, following the plebiscite of 11 July 1920, remained part of Germany and was incorporated into the province of East Prussia (as the ‘Administrative District of West Prussia’) – passed to Poland without a referendum. The area ceded amounted to 17,750 km².

- The Soldau area (south-western East Prussia) was transferred to Poland without a referendum; area: 500 km².

- The Hultschin region/Hlučínsko/Kraik hulczyński ( Upper Silesia) was transferred to Czechoslovakia without a referendum; the area covered 330 km².

- Eastern Upper Silesia (area 3,241 km²): Following the referendum held on 20 March 1921, in which approximately 60 per cent of those eligible to vote had voted for Germany and approximately 40 per cent for Poland, the relevant League of Nations commission decided to to divide the territory in accordance with a provision set out in the Treaty of Versailles. This decision, as well as the demarcation of the border – which resulted in the majority of the coal mines and industrial facilities lying within Polish territory – reflected the preference shown, particularly by France, for its Polish ally. Although a border demarcation more favourable to Germany had initially been envisaged, Polish armed groups attempted, during the third of the Silesian Uprisings (2 May – 5 July 1921; the other two having taken place in 1919 and 1920), to enforce Poland’s far-reaching territorial claims by force. The Allied troops stationed there to maintain order offered little resistance; however, the ‘Upper Silesian Self-Defence Force’, formed from Freikorps units, pushed back the Polish units, particularly during the Battle of St Ann’s Mountain/Góra Świętej Anny ( 21–27 May 1921). The final demarcation of the border largely corresponded to Polish wishes. Nevertheless, the German–Polish Agreement on Upper Silesia, concluded in Geneva on 15 May 1922 for a period of 15 years, guaranteed important protective rights for national minorities on both sides.

- In 1919, Danzig and its surrounding area, covering an area of 1,966 km², were declared the ‘Free City’ under the protection of the League of Nations. However, the Polish state, which had laid claim to Danzig even though only around five per cent of its inhabitants were Polish, was granted extensive economic and military rights within this newly created state (particularly in its port) and represented it externally, whilst the German Empire, as the mother country of 95 per cent of Danzig’s population, lost all sovereign rights in the city.

At that time, the following came under League of Nations administration:

- the Saar region (Saarland; area 1,910 km²) from 1920 to 1935 (de facto under French occupation). France attempted to bring the region under its economic, political and cultural control; however, in accordance with the result of the referendum held on 13 January 1935 (over 90 per cent in favour of Germany), it was returned in full to the Reich on 1 March of the same year.

- the Memel region (Memelland; area 2,848 km²) from 1920 to 1923 (also under French occupation). It was occupied in 1923 in a surprise raid by Lithuanian units and subsequently incorporated into Lithuania; the League of Nations approved this action. On 22 March 1939, following an ultimatum issued by the German Reich to Lithuania, the Memel region once again became German territory.

The Rhineland, including several bridgeheads on the eastern bank of the Rhine, was occupied by the Western Powers from 1918 to 1930 and declared a demilitarised zone under the Treaty of Versailles (including a 50-kilometre-wide strip on the eastern bank), but remained German territory throughout. This measure served primarily as a means of securing German reparations payments. Following the signing of the Treaties of Locarno in 1925, the occupation – which could have lasted until 1935 at the latest – was gradually lifted from 1926 onwards and – following the signing of the Young Plan, which was intended to settle the reparations payments once and for all – brought to an end on 30 June 1930. In 1922, the parts of Posen and West Prussia bordering other Prussian provinces to the west, which remained part of Germany, were combined to form the new province of Grenzmark Posen-West Prussia, with its capital at Schneidemühl/Piła (area 7,695 km²). It existed until 1938, when it was dissolved and its districts were incorporated into the surrounding provinces of Pomerania, Brandenburg and Silesia.

Following the Nazi regime’s seizure of power in 1933, numerous territorial changes took place, initially through peaceful means and, from 1939, by military force. The return of the Saarland to German sovereignty in 1935 and the so-called remilitarisation of the Rhineland in 1936 – that is, the re-establishment of German military structures in this region, which had been demilitarised under the Locarno Treaties – did not , strictly speaking, constitute territorial expansions. Such territorial expansions, however, did occur with the annexation of Austria (‘Anschluss’) on 13 March 1938 and with the annexation of the predominantly German-inhabited areas of Czechoslovakia (‘the Sudetenland’) following the Munich Agreement concluded on 29 September 1938 between Germany, Great Britain, France and Italy. Whilst these still constituted demands for territorial revision that could be justified on ethnographic grounds from the German side, the occupation of the so-called ‘remainder of Bohemia’ and the subsequent proclamation ofthe “Protectorate of Bohemia and Moravia”as part of the Greater German Reich on 15 March 1939 marked an expansion beyond the German settlement area and the beginning of a geostrategically motivated policy of expansion. After the outbreak of war in September 1939, subsequent territorial policy became complex and depended on the specific political objectives in each respective area. Immediately following the invasion of Poland, the Free City of Danzig was reintegrated into the Reich on 1 September 1939; shortly afterwards, on 26 October 1939, it was merged, together with the territory of the Polish Voivodeship of (Greater)Pomerania (Województwo Wielkie Pomorze, since 1938) and the East Prussian administrative district of West Prussia, to form the Reichsgau Danzig-West Prussia. On the same day, the Reichsgau Posen (renamed the Reichsgau Wartheland from January 1940) was established on the territory of the former Greater Poland Voivodeship (Województwo Wielkopolskie). The Reichsgaus were regarded as Reich territory directly subordinate to the Reich leadership (represented by the Reich governors), and thus without even a formal regional level; the NSDAP party districts, which were established to correspond exactly with these areas, were of great importance for the political and administrative integration of these territories. The status of the General Government, which was also established on 26 October 1939 from the remaining German-occupied Polish territories, remained unclear. It was not annexed, and its temporary designation as a ‘neighbouring territory of the Reich’ provided no clear constitutional definition. The civil authorities under Governor-General Hans Frank (1900–1946) operated in what was effectively a legal vacuum, where neither international law nor the informal conventions that were at least partially observed in occupied Western Europe applied. For this reason, and in view of the nature of Nazi occupation policy, the General Government could be described as a ‘semi-autonomous colonial territory’.

As indicated, a different approach was taken with regard to the territories on the western border that were occupied following the Western Campaign in May/June 1940. Whilst Eupen-Malmedy, which had been ceded to Belgium in 1919, was annexed, Luxembourg, (German) Lorraine and Alsace were initially placed under German civil administration only (so-called CdZ territories, ‘Head of Civil Administration’); this was linked to Hitler’s (1889–1945) intention to treat his Western European opponents relatively leniently and to keep his options open regarding alliances. At the same time, these territories were incorporated into the NSDAP’s expanded Gau structure: Eupen-Malmedy into the Gau Cologne-Aachen, Luxembourg into the Gau Moselland, Lorraine into the Gau Westmark (together with the Saarland and the Palatinate) and Alsace into the Gau Baden, or from then on the Gau Baden-Alsace. The long-term plan was to convert the Westmark and Baden-Alsace Gaus into Reichsgaue (in the case of Baden-Alsace, as the ‘Reichsgau Upper Rhine’); however, this did not come to pass by 1945. Following the victory over Yugoslavia in April 1941, the CdZ territories of Carinthia and Carniola – formerly part of Austria – bordering the Reich, as well as Lower Styria, were established; these were also earmarked for subsequent annexation. The Bialystok/Białystok district, formed from former Polish and Belarusian territory following the German attack on the Soviet Union in June 1941, constituted a special case. Administratively, it was placed under the authority of the Gau of East Prussia and constituted the only CdZ territory within the Eastern Front; preparations for its full incorporation into the Reich were systematically carried out until the German retreat in the summer of 1944.

The German defeat in the Second World War in 1945 led not only to the loss of all territorial gains made since 1938, but also to the occupation of the whole of Germany and the loss of the eastern territories within the 1937 borders. By early 1945, the advancing Soviet forces and the Polish units accompanying them had occupied the provinces of East Prussia, West Prussia (including Danzig), Pomerania and Silesia up to the Oder–Neisse line; they began to expel the German population who had not yet fled and declared the occupied German territories to be Soviet or Polish national territory. These unilateral claims – which were turned into faits accomplis through the establishment of Polish and Soviet military and civilian structures, as well as through resettlement measures – were invalid under international law. A formal interim solution was reached at the Potsdam Conference (17 July – 2 August 1945), at which the Western Powers accepted the placement of the German eastern territories under Soviet or Polish administrative sovereignty; this included consent to the ‘orderly and humane transfer’ of the Germans still remaining east of the Oder and Neisse rivers to the remaining German territory. This arrangement did not constitute recognition under international law of the Oder–Neisse line as Poland’s western border, as the final demarcation of the border was to be reserved for a general peace conference, which never took place as a result of the Cold War. The GDR’s recognition of the border in the Görlitz Agreement of 6 July 1950 was rejected by the Federal Republic as illegitimate. With the declaration of renunciation of the use of force in the Warsaw Treaty of 9 December 1970 and in the CSCE Helsinki Final Act signed on 1 August 1975, the Oder–Neisse border was de facto recognised by the Federal Republic, even though this did not yet imply a definitive relinquishment of territory. This, and thus the final settlement under international law, was only achieved after German reunification in the German–Polish Border Treaty of 14 November 1990, which had been laid down as binding in the Two-Plus-Four Treaty of 12 September 1990. The status of northern East Prussia (as Kaliningradskaya oblast’), which was conquered by the Red Army in 1945, as part of the Soviet Union or Russia is not based on any comparable provision under international law; following the decision in the Potsdam Agreement to place the territory under Soviet administration, it was annexed on 17 October 1945. By defining the territory of a united Germany as comprising the territories of the Federal Republic, the GDR and Berlin in the Two-Plus-Four Treaty (whereby the question of the continued existence of the Reich within its 1937 borders was no longer discussed), the two German states implicitly recognised this status quo in 1990. Memel was incorporated into the Lithuanian Soviet Socialist Republic in 1945 and has been part of the Republic of Lithuania since 1991.

In the West, too, following 1945 – apart from the return of Alsace-Lorraine to French control – there were cessions of German territory to neighbouring states, albeit for the most part only temporary. As it had done after the First World War, France once again attempted to secure the Saarland for itself; to this end, it pushed for its separation from the French occupation zone in 1946 and for the adoption of a separate Saarland constitution in 1947. De facto, the region was controlled politically and economically by France. Under the terms of the Paris Treaties, Federal Chancellor Konrad Adenauer (1876–1967) was prepared in 1954 to negotiate the so-called (second) Saar Statute with France, which would have ‘Europeanised’ the Saarland until the conclusion of a peace treaty – in effect, permanently removing it from the German federal system. However, this option was rejected by two-thirds of the Saarland population in a referendum on 23 October 1955; consequently, the region became the tenth Federal State of the Federal Republic of Germany on 1 January 1957. Also initiated by France was the Ruhr Statute of 1949, which provided for joint control of the West German coal and steel industries by the Western Powers and the Federal Republic, which was then in the process of being established. Initially, as in the case of the Saar, France sought to separate the region from Germany; however, the USA and the United Kingdom opposed this on the grounds of economic reconstruction. The Ruhr Statute was replaced in 1951 by the European Coal and Steel Community (ECSC). The Benelux countries also attempted, after 1945, to secure compensation for the German occupation through territorial cessions. Whilst Belgium and Luxembourg asserted only minor, largely symbolic claims to German border districts, the Netherlands made territorial claims along the shared border covering an area of approximately 1,840 km², which included, amongst others, Borkum, East Frisia, the Emsland, the County of Bentheim and parts of the cities of Osnabrück, Münster, Aachen and Cologne. Here, too, political pressure from the major Western powers ensured that the Federal Republic – which was needed as an ally – was spared more severe losses; as a result, after 1949, only territories totalling approximately 70 km² came under so-called Dutch mandated administration, which did not constitute annexation. In 1963, these territories, with the exception of a few very small strips of land, were returned to Germany. Belgium had already returned all its occupied territories in 1958 – including a territorial exchange – whilst Luxembourg did so in 1959.

Following the end of the Holy Roman Empire in 1806, brought about by Napoleon (1769–1821), the German states—which were then nominally sovereign—divided into, on the one hand, the members of the Confederation of the Rhine, which was directly subordinate to France, and, on the other, the powers of Austria and Prussia, which were formally allied with Napoleon on an equal footing. In the course of the Wars of Liberation from 1813 to 1815, Napoleon’s German vassal states did indeed break away from him one after the other; however, they insisted on their autonomy and rejected the idea of German unification. The German Confederation, founded in 1815, indirectly continued the imperial tradition, but did so explicitly within a European framework and on the basis of the monarchical principle. Whilst one of the Confederation’s primary aims was initially to suppress nationalist and liberal aspirations in Germany, by 1848–49 it had become the legal and political basis for the attempt to re-establish a democratic empire. A key factor in this was the shift in the concept of the empire from a universalist, supranational interpretation to a national one centred on the German people. This process, driven primarily by bourgeois circles, had already begun in the late 17th and 18th centuries in the wake of the secession of most non-German territories from the Holy Roman Empire, and was completed in the second half of the 19th century.

The integration of the German Confederation into the political strategy of Otto von Bismarck (1815–1898) was essential to the ultimate success of German unification, as it made it possible to free Prussian policy from the stigma of particularist power-seeking and to rally the bourgeois public in Prussia and the other German states behind Bismarck. At the same time, the experiences of 1848–49 had shown that unification would only be possible with the consent of the other great powers and/or through armed conflict against them. The scepticism of the Liberals – who were strongly represented in the Prussian Landtag after 1860 – towards the ‘authoritarian modernisation’ pursued under the New Course and the power-politics-driven unification policy in Germany was expressed above all in the well-known military conflict. Ultimately, Bismarck was only able to resolve this conflict in his favour as a result of the successes he had achieved. The popular joint campaign by Prussia and Austria against Denmark in 1864 illustrated for the first time this rapprochement between the bourgeoisie and the civil-military state authority, which was still predominantly led by the aristocracy. The ‘moral victories’ Bismarck had hoped for did indeed benefit Prussia above all, whilst the incompatibility between the Habsburgs’ dynastic interests and the quest for German national unification became increasingly apparent. An important factor in foreign policy was that, whilst England and Russia closely monitored developments in the German Confederation from the perspective of maintaining stability, they accepted Bismarck’s assurances that his policies would realise the Germans’ right to national unity in a form that would also accommodate the security interests of the other powers. In any case, in Saint Petersburg/Saint-Pétersbourg/Leningrad and London, the France of Napoleon III (1808–1873) was generally perceived as the disruptive factor.

In 1807, Prussia – which had been defeated by Napoleon – owed its – albeit reduced – continued existence largely to the intervention of Tsar Alexander I (Aleksandr I, 1777–1825), who wished to establish a buffer between the Russian Empire and expansionist France. The Prussian–Russian alliance concluded against Napoleon in 1813 contributed significantly to the salvation of the Hohenzollern state, but after 1815 also led to Prussia’s long-term dependence on Russia, as the country had been exhausted by the French occupation and the burdens of war. Within the German Confederation, Austria once again assumed the leadership of the German states. ‘Third Germany’ was primarily concerned with maintaining its position vis-à-vis the two great powers, and continued to maintain close ties with France and Western Europe. In Prussia, the memory of the country’s reconquest from the east cemented the special status of East Prussia, with its coronation city of Königsberg/Kaliningrad and the other old Prussian provinces. In Prussian domestic politics, the ‘Polish question’ took on increasing significance, even though the territory acquired from the Partitions of Poland in 1815 had been greatly reduced. In the provinces of Posen and West Prussia, it was initially the Polish nobility who, encouraged by the preceding phase of the Duchy of Warsaw created by Napoleon, sought to regain their position as the ruling class in a Polish state. Consequently, the social and functional privileges offered by the king were not enough for them; rather, they supported the uprisings in Russian Poland in 1830–31 and 1863–64 and also hatched corresponding plans within Prussia, for example in 1846.

The revolution that broke out in 1848 revealed the conflicting interests of Germans and Poles in the Prussian eastern territories, which lay hidden behind the slogan of ‘friendship among nations’—a slogan based, amongst other things, on their shared rejection of Russian policy. The Poles attempted to gain exclusive control over the Province of Posen, to the detriment of Germans and Jews; their military uprising was crushed by Prussian troops. The resulting shift away from the ‘enthusiasm for Poland’ of the Vormärz period was also evident in the proceedings of the German National Assembly at St Paul’s Church in Frankfurt; from then on, German and Polish national interests were to appear to many as irreconcilable. Against the backdrop of a shift from a primarily emancipatory form of nationalism to an integral and geopolitical one, the Liberals’ alignment with the Prussian government’s line took place in the 1870s, partly for reasons of strategic security. Russia’s – more or less – benevolent neutrality proved to be an important factor in Bismarck’s political strategy. In addition to the close ties between the two dynasties, Russian displeasure at Austria’s intervention on behalf of the Western powers in the Crimean War also played a part. These factors, together with the assurances mentioned, prompted the Tsar to accept the ‘revolutionary’ aspects of Bismarck’s policy, namely the mobilisation of the bourgeois public and the deposition of friendly ruling houses. Russia remained neutral in 1866 and, in 1870, prevented Austria from intervening on France’s behalf through unequivocal threats. In 1871, the Second Reich replaced the German Confederation – which, as a zone of European equilibrium, was openly exposed to foreign influences – with a sovereign nation state that took Prussia’s place as an equal member of the concert of powers.

In terms of domestic policy, the German Empire represented a compromise between the values and interests of the princes on the one hand – who, through their representatives in the Bundestag, remained the nominal holders of sovereignty – and those of the bourgeoisie on the other. The latter played a decisive role in shaping the dynamic development of the new nation state in the fields of the economy, science, culture and education, whilst at the same time fostering a culture of political debate and decision-making within the Reichstag that continually pushed back the de facto limits of parliamentary power within the constitutional monarchy. The integration of the working class – which was essential to economic development – became the primary social task; its political arm, the SPD, gradually moved towards a reformist course and, by 1912, had become the largest parliamentary group in the Reichstag. As a result, the Reich presented the often contradictory image of a country that was outwardly traditionalist and still dominated by the nobility, yet was modern at heart and, in many respects, at the forefront of general European development; in this respect, it resembled Great Britain and other Western and Northern European monarchies. Owing to the growing ethno-cultural concept of the nation, national and ethnic minorities (including Poles, Danes, Alsatians and Lorrainers) came under increased pressure to assimilate. The main structural problems of the Empire, however, were, on the one hand, the contrast between the industrial regions, situated primarily in the west, and the agrarian eastern provinces, and, on the other hand, the tension between the ‘particularist’ interests of the Prussian monarchy and the ever-increasing momentum of the Empire as a nation-state. In terms of foreign policy, the Empire was the last of the major European nations to begin acquiring colonies in the 1880s, and under Wilhelm II (1859–1941) pursued the so-called ‘Weltpolitik’, which was intended to secure Germany’s equal standing with Great Britain, Russia, France and the USA. The conservative policy of balance cultivated by Bismarck to isolate France lost its effectiveness after 1890, as Russia and Britain felt a growing rivalry with the young Empire. Consequently, a Franco-Russian alliance formed, whilst Germany found itself confined to the Triple Alliance with Austria-Hungary and Italy. The Entente Cordiale of 1904 and the Anglo-Russian Entente of 1907 left Germany strategically ‘encircled’, a situation it sought to counter by forming a strategic axis via Bulgaria into the Ottoman Empire (‘Berlin–Baghdadrailway”) via Bulgaria.