This article will explain why Russia annexed Crimea and is destabilizing eastern Ukraine. To do this, three different theoretical approaches on various levels of analysis will be used. It will be examined how far the expansion of NATO, as well as that of the European Union (Theory of Neorealism), was a motive for Russia’s action. NATO’s enlargement is analysed predominantly. In addition, politicalpsychological motivations of the Russian leadership are considered. But it is also analysed whether Russia’s pure power interests have played a role (Theory of Realism). The focus here is on the Russian naval base in Crimea. It is necessary to examine whether preserving its fleet in the Black Sea was a motive for Moscow to annex the Crimean peninsula.

中文翻译：

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俄罗斯与乌克兰危机：考虑到北约和欧盟的扩大，对俄罗斯的行为进行多角度分析

本文将解释俄罗斯为何吞并克里米亚并破坏乌克兰东部的稳定。为此，将在不同的分析级别使用三种不同的理论方法。将研究北约以及欧洲联盟（新现实主义理论）的扩张是俄罗斯采取行动的动机。主要分析北约的扩大。此外，还考虑了俄罗斯领导人的政治心理动机。但同时也分析了俄罗斯的纯权力利益是否发挥了作用（现实主义理论）。这里的重点是克里米亚的俄罗斯海军基地。有必要检查保存其在黑海的舰队是否是莫斯科吞并克里米亚半岛的动机。