When I studied history I was made to read a lot of European history, with UK syllabuses largely or wholly ignoring the histories of the USA and Asia. It was a depressing study to read of a continent rent between Catholics and Protestants for four centuries and between communists and fascists for a fifth. The history was disfigured by the successive imperial ambitions with planned invasions of Britain by Italy, the Norsemen, Spain, the Holy Roman Empire, France and Germany , as successive efforts were made to create a Europe united by conquest and suppression.
I came away with the realisation that England, later the UK, had suffered badly from its interventions in Europe. We had been invaded and put into slavery by the Italians when they were called Romans. We had been pillaged and occupied by Scandinavians called Vikings or Norsemen. We had been subjugated with lands and businesses stolen by the French after the Norman invasion as they enforced feudal serfdom. We had in the sixteenth century to defeat the mighty Spanish empire as they launched a major invasion. In the eighteenth and early nineteenth centuries we needed to defeat another big French attempt to subjugate us. Twice in the twentieth century we had to defeat German efforts at conquest.
Part of the reason I opposed our membership of the EEC, later the EU, was my knowledge that attempts at European Union had always turned out badly in the past. Introducing a European army was unlikely to make a more peaceful or secure Europe. The Holy Roman Empire superimposed above the German states had not brought stability, but did become a fighting unit in its own interests. The EU has more now calling for an EU army. The EU has made moves to common weapons systems and procurement, undertakes common actions militarily and wishes to extend its defence competencies.
The UK has always been generous to the continent. Our predecessors spilt much blood and treasure stopping the spanish conquest of the Netherlands and other Protestant states. They did much to prevent Napoleon dominating most of Europe. The UK stood alone against Germany in 1940 before the US entered the war. In the EU we made a large financial contribution and opened up our market to their exports, running a huge deficit, as their market opening was one sided.They would not open their services markets to help us.
Today the US has rightly challenged European members of NATO and the EU to do more for our own defence. The UK should be no part of a common defence of the EU and its borders. As they expand eastwards they must provide the forces for their own security. We should meet our NATO obligations to fellow NATO members just as we need their support and guarantee. It is feasible to keep the USA in NATO as long as we and other members do a bit more to provide both military and industrial capacity to resist and deter invasion. It is not feasible to expect the US to provide defence cover for an expanding EU as they add non NATO members.