How did Germany claim self-defense in WW1?

Question

WW1 broke out after a series of ultimatums and warnings against each other. However, I understand that every power claimed that the other powers were acting against its interests, and it was participating in the war only for self-defense.

I can understand these claims from the points of view of Austria-Hungary, Russia, and even France. Britain participated protesting against the violation of neutrality of Belgium, so even that claim is clear (at least it's not false, though it might have been just an excuse).

However, how could Germany make this claim, as it had given ultimatum to Russia against its military mobilization? How did Germany convince itself or its population that this war was only for self-defense?

Answer 1

By naming Russian mobilisation as the initial aggression.

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One needs to look no further than the German declaration of war itself. That document succinctly laid out Berlin's position that the Russian mobilisation was an existential threat as well as an act of aggression towards Germany. Presenting Germany as a peaceful mediator, it claims that:

[Russia] proceeded to a general mobilisation of her forces both on land and sea. In consequence of this threatening step ... the German Empire was faced by a grave and imminent danger. If the German Government had failed to guard against this peril, they would have compromised the safety and the very existence of Germany. The German Government [therefore insisted] upon a cessation of the aforesaid military acts. Russia having refused to comply [have shown] that her action was directed against Germany

The document ended by explicitly portraying the Germany as answering a challenge to fight. A challenge which, according to the German government, Imperial Russia had issued by mobilising.

His Majesty the Emperor, my august Sovereign, in the name of the German Empire, accepts the challenge, and considers himself at war with Russia.

Germany thus portrayed herself as a victim of Russian aggression, and her subsequent military actions "self-defence".

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The German argument was not a stretch to make in 1914. Countries did not (and do not) mobilise for fun. In an age of mass conscript armies, mobilisation was the key stage in the ramp up to war. The tight coupling of mobilisation with war was such that it was effectively regarded as an act of war in and of itself. In Russia specifically,

The idea that mobilization was not a peaceful act but 'the most decisive act of war' had been present in the thought of Russian officers since 1892. The 1912 the European military districts were told to regard mobilization as the opening of hostilities.

_{- Strachan, Hew. The Outbreak of the First World War. Oxford University Press, 2004.}

Moreover, Russia was allied to France by an accord that was understood, by both sides, to mean that mobilisation guaranteed a war on two fronts for Germany.

General N. N. Obruchev, Russia's signatory, explained [Article 2 to mean], 'this mobilisation of France and Russia would be followed immediately by positive results, by acts of war, in a word would be inseparable from an "aggression"'. Or as France's counterpart to Obruchev, General Raoul de Boisdeffre, put it after signing the accord, "the mobilization is the declaration of war."

_{- McMeekin, Sean. July 1914: Countdown to War. Basic Books, 2014.}

In the mindset of 1914 Europe, therefore, the Russian mobilisation essentially meant war. This also meant that the German ultimatum for Russia to cease its mobilisation would not have detracted from the self defence argument. If anything, it strengthened it - Germany could present itself as having explored all changes for peace before before "accepting" the Russian challenge to fight.

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Disclaimer: Whether the German rationale is objectively correct is of course an entirely different matter. This answer also no commentary on the (in)accuracy of the other Great Powers' claims for a righteous casus beli, either.

Answer 2

The short answer is that, if Germany sat and waited while Russia mobilized, the Germans believed they would be crushed between France and Russia.

Imperial Russia was considered to be a powerful nation because they could put so many men in the field. Russia's inability to properly equip or supply them was not properly understood.

The German war plan was to overwhelm France before Russian strength could be massed against Germany. France also knew the odds and directed railway investment into Russia as long as the railways led to the European frontier [Tuchman, Guns of August], in order to reduce the time it would take for Russia to mobilize and apply her forces against Germany.

Answer 3

It has been a long time, and I have already accepted an answer, and I am satisfied with it. But I'm reading The Guns of August right now, and I discovered following small facts. It's not a very important things, because the nations were already set on a collision course, but I think they are worth noting anyway.

Germany had developing Schlieffen Plan against France for several years, in which France was to be attacked via Belgium (and Luxembourg). Germany had made repeated attempts, direct or otherwise, to gauge the British response if Germany violated Belgian neutrality. Britain was however committed to the neutrality and made it clear (to both Germany as well as France, but in different tone) that whoever violates Belgian neutrality would not have British support.

Secondly, when it was clear that the war on the Eastern Front was inevitable in the last couple of days of July 1914, because of Austria-Serbia-Russia crisis, German high command (especially the Kaiser) seriously contemplated abandoning the Schlieffen Plan, and attacking Russia instead. They even asked France whether it would remain neutral in a Russo-German war, but it replied that "France would take an action in its own interests". This formal interaction, in my opinion, gives some kind of legitimacy to the war against France. In either case, von Moltke, who himself was very much committed to the plan, managed to convince Kaiser that the military commitments to the plan were irreversible, and thus Germany entered into a war on two fronts.

Source: The Guns of August by Barbara Tuchman.