Fifty years after the Rome Treaty that initiated an era of cooperation amongst warring states, 27 countries have joined the European Union and more are waiting in the wings. The EU is not intended to replace member states. But they have set up common institutions to which they delegate some of their sovereignty so that Europe-wide decisions on specific matters of joint interest can be made. Since 1993, under the Maastricht Treaty, the EU has been developing a common foreign and security policy to enable joint action when the bloc's interests are at stake. As it deals with terror, international crime, drug trafficking, illegal immigration, global issues like the environment -- and now challenges such as Kosovo's declaration of independence -- diversity remains the hallmark of the Union of half a billion people.