This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

Q: Warsaw was occupied by Germany from 4 August 1915 until November 1918. The Allied Armistice terms required in Article 12 that Germany withdraw from areas controlled by Russia in 1914, which included Warsaw. Germany did so, and underground leader Piłsudski returned to Warsaw on 11 November and set up what became the Second Polish Republic, with Warsaw the capital. In the course of the Polish-Bolshevik War of 1920, the huge Battle of Warsaw was fought on the eastern outskirts of the city in which the capital was successfully defended and the Red Army defeated. Poland stopped by itself the full brunt of the Red Army and defeated an idea of the "export of the revolution".

A: How long was Warsaw occupied by Germany?
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Q: Regardless of the ability of the Luftwaffe to win air superiority, Adolf Hitler was frustrated that it was not happening quickly enough. With no sign of the RAF weakening, and Luftwaffe air fleets (Luftflotten) taking punishing losses, the OKL was keen for a change in strategy. To reduce losses further, a change in strategy was also favoured to take place at night, to give the bombers greater protection under cover of darkness.[b] On 4 September 1940, in a long address at the Sportspalast, Hitler declared: "And should the Royal Air Force drop two thousand, or three thousand [kilograms ...] then we will now drop [...] 300,000, 400,000, yes one million kilograms in a single night. And should they declare they will greatly increase their attacks on our cities, then we will erase their cities."

A: The Luftwaffe air fleets were taking what kind of losses?
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Q: Another energy-related concept is called the Lagrangian, after Joseph-Louis Lagrange. This formalism is as fundamental as the Hamiltonian, and both can be used to derive the equations of motion or be derived from them. It was invented in the context of classical mechanics, but is generally useful in modern physics. The Lagrangian is defined as the kinetic energy minus the potential energy. Usually, the Lagrange formalism is mathematically more convenient than the Hamiltonian for non-conservative systems (such as systems with friction).

A:
What is another energy-related concept?
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