The idea of a common EU security policy, originating from the so called Pleven Plan announced in October 1950, has experienced many ups and downs. Never fully realized, it is now subject to two opposing impulses. The first was the dramatic deterioration of the European security environment caused by Russia’s aggression against Ukraine; the second, President Trump’s announcement that the American “security umbrella” over European NATO members would be conditional on their radical increase in defence spending. Analysing the United States’ attitude toward its European allies, the article points out that throughout nearly the entire existence of NATO, this attitude has also been subject to significant fluctuations. This attitude results from the interplay of two conflicting needs: maintaining an adequate level of the United States’ own military equipment resources and retaining the ability to influence the decisions of its allies. The strength of this influence, apart from the level of the threat environment and the state of American resources, is also conditioned by the allies’ capacity to acquire military equipment. The current international situation has made most European NATO states realize that their armed forces are unable to fulfil their primary task – defending their own territory – and that domestic defence industries cannot rapidly supply the necessary equipment for this purpose.