Political polls taken before major elections are examples of research. case study survey experimental correlational

That would be survey research.
Surveys are used for the political polls as they are very good and appropriate for this kind of research as they consist of questions that have the aim of eliciting the specific information and data from the people about a particular subject.  Surveys can take a wide variety of forms be that a simple phone interview or a kind of online survey.

Towards the end of the 19th century, Europe was a territory convulsed by constant confrontation between the great powers. The Russian expansionism, on the one hand, and the constant tensions with France, on the other, caused the German Empire to see the need to rearm after the unification in 1871.

The army became a central element of emerging imperial patriotism. Criticism of the military was seen as unpatriotic. During this period the Schlieffen concept emerged for a possible war on two fronts against France and Russia, and the armed forces were reinforced in the face of such a hypothesis.

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