Final answer:
Since World War II, Europe has not experienced a conflict involving major powers of similar scale and devastation, but it has faced various military conflicts and political challenges. The EU and the UN were established in the aftermath to promote stability and prevent such wars in the future.
Step-by-step explanation:
The phrase 'Europe has not seen a war of this kind since 1945' typically refers to the absence of a war involving the major powers in Europe of the scale of World War II. This conflict, the most devastating in European history, involved widespread military engagements, significant civilian casualties, and a complete mobilization of national resources. Since then, Europe has experienced periods of tension and military conflict, but not of the kind that encompasses a world war.
In the post-Cold War era, Europe has seen the emergence of a politically freer environment with the reduction in fear of nuclear war. However, several military conflicts have occurred in Eastern Europe and the former Soviet Union. Additionally, despite the unifying efforts of the European Union (EU), Europe continues to face challenges, such as political divisions, financial crises, and social pressures from migratory movements.
The war's aftermath brought significant changes to international relations with the introduction of the United Nations (UN) and collective security agreements like NATO. The establishment of the UN in 1945 aimed to foster international cooperation and prevent future conflicts on such a devastating scale.