[en] The author of a first note discusses the deterrence game which can be observed about the Ukrainian crisis on the Russian (provocative and other statements), and on the western side. He also tries to assess the risk of a use of nuclear weapons as it appeared in different statements, and tries to highlight the consequences for the Russian deterrence (a strengthened position) and for the western deterrence (failure of economic deterrence, a somehow weakened nuclear deterrence, a validated and strengthened extended deterrence from a Nato's point of view), and the consequences in terms of non-proliferation and disarmament. The author of the second article outlines the frequent presence of a nuclear signal in statements of Russian authorities (notably by Putin ever since the Crimea crisis), and in the use of some dual systems. She also analyses the relationship between the war in Ukraine and the Russian nuclear doctrine, and questions the attitude which appears to be a kind of intimidation based on a managed drift control