With the geopolitical landscape in a flux, what is Europe's roadmap for the future?

Does it need to rethink its collective security and defence policy? And by doing so, will it create an impenetrable EU fortress?

The origins of a collective defence policy date as far back as the 1940s. It started with the Treaty of Brussels, signed in 1948 and amended in 1954 in Paris. It was implemented by a new military organization, the Western European Union. The most important idea of the Treaty was in article 5: The idea of coming to the aid of another under attack.