Greetings! This is a most interesting question you have put forwards, and it is something which remains a topic of historiographical importance within the First World War. I would highly recommend, if possible, that you pursue further reading with that hallmark work by Fritz Fischer, Germany's War Aims in the First World War (translated of course, from the original: Griff nach der Weltmacht: Die Kriegszielpolitik des kaiserlichen Deutschland 1914–1918). It was this publication which reignited the whole historiographical debate on what exactly the German Empire of 1914 wished to achieve when they issued that "blank cheque" to Austria-Hungary. With that recommendation and preamble aside, let's begin.

Prussia Ascends

"Mit einem Worte: wir wollen niemand in den Schatten stellen, aber wir verlangen auch unseren Platz an der Sonne." (in one word: We wish to throw no one into the shade, but we also demand our own place in the sun.).^(1)

The quote above was made by Secretary of State of Foreign Affairs Bernhard von Bulow in December of 1897 to the German Reichstag (essentially their parliament). It echoes, in essence, the ultimate dream of Prussia (and then Germany) going into the 20th century. The German government was new to the game of Empires, and it believed that if Germany were to continue her rise as a continental and then global power, she required colonies of her own. This belief would soon become known as Weltpolitik (world politics), in which the German government deliberately sought to expand the influence of this new European power within and beyond the continent, in the hopes of becoming a new Weltmacht (world power). Historian Michael Howard on this pride in the imperialist system:

It [the German Empire] had every reason to be ambitious. It constituted a nation over sixty million strong with a superb heritage of music, poetry, and philosophy, and whose scientists, technologists, and scholars (not to mention soldiers) were the envy of the world... The Germans prided themselves on a uniquely superior culture that held the balance between the despotic barbarism of their eastern neighbours and the decadent democracy of the West."^(2)

To the Germans, their main rival (and obstacle) in this quest for world power was the British Empire, which at the time was the largest and possessed large influence all over the world. This "British problem" as I shall phrase it henceforth, would be a key contributor to the German aims in World War 1.

The Imperium of Europe

When the First World War began, the German High Command was still pondering the British problem. For the most part, they had left it to the Kaiserliche Marine (the German Empire's Navy) to deal with the British threat. This of course entailed a naval confrontation somewhere in the North Sea or even the Channel, but the High Seas Fleet did not possess the perceived strength to take on the Royal Navy's Grand Fleet based in Scapa Flow and later the Firth of Forth. German military planners for their part did not concern themselves too much with the threat of a British Expeditionary Force on the continent, but they did fear (as in the days of Napoleon) a prolonged war in which Britain's impregnability as an island nation would be exploited to force a peace (something Germany was not willing to endure, as it had taxed Napoleon in his efforts a century ago).

As the war dragged on and hopes of a swift victory were dashed, within the German Empire there were various camps forming with regards to German war aims. On the larger scale, we have the supporters of national self-sufficiency, and on the other side the imperialists of the Pan-German stamp. Historian Wolfgang J. Mommsen best describes what the first of these groups believed in:

To the [national self-sufficiency group], the true purpose of the war was the victorious defense of the German Reich against a world of enemies; hence their positive war aims were directed solely towards ensuring the security of the empire.^(3)

Whereas a contemporary account in 1915 by theologian and philosopher Ernst Troeltsch, who himself was a member of the national self-sufficiency camp, best describes the stance of the imperialists:

"What a German victory should aim to achieve is the permanent enfeeblement of the great world powers on its borders, namely the British and Russian empires; this would also remove for ever the French threat to Germany. German world power must supplant [replace] these weakened empires."^(4)

Even within the imperialist camp, also known as the "annexationists", there were divisions. The "anti-imperialists" such as Chancellor von Bethmann Hollweg, believed that a "weak-kneed" peace was ideal to avoid further German suffering, and the right-wing "total annexationists", who echoed the nationalist sentiments of Bulow and the other Prussian nobility by pushing for German confidence in taking territory everywhere it could. It was this unyielding commitment to expansion which doomed German peace efforts in 1915 with the Belgians and 1916 with the Dual Entente (Britain and France).

What did the Germans want exactly with victory? A hard question to be sure, but Fischer believes that the German vision of a Mitteleuropa (Middle Europe) and Mittelafrika *(*Middle Africa) embody the main rhetoric of German war aims. They wished to create a Europe and Africa with Germany as the key nation-state in the former and influencer (and perhaps coloniser) in the latter.

Hope this response helps, and let me know if you have any follow-ups on the matter!

Sources:

[1]: Sourced from Fürst Bülows Reden nebst urkundlichen Beiträgen zu seiner Politik. Mit Erlaubnis des Reichskanzlers gesammelt und herausgegeben von Johannes Penzler. I. Band 1897–1903. Berlin: Georg Reimer, 1907. p. 6-8. (Though easily found in any online publications or academic texts regarding the German Imperialist Policy)

[2]: Howard, Michael: The First World War: A Very Short Introduction, (Oxford Press, 2007)

[3]: Mommsen, Wolfgang J. "The Debate on German War Aims." Journal of Contemporary History 1, no. 3 (1966): 47-72. Accessed January 29, 2021. http://www.jstor.org/stable/259935.

[4]: Quoted in Mommsen, Wolfgang J. "The Debate on German War Aims."

Epstein, Klaus. "German War Aims in the First World War." World Politics 15, no. 1 (1962): 163-85. Accessed January 29, 2021. https://www.jstor.org/stable/2009574.