What is it? The Schengen agreement, named after the village in Luxembourg where it was signed in 1995, allows for passport-free travel through 26 European countries, including most members of the EU.

What did it help achieve? The agreement succeeded in fostering greater economic growth across the region by easing the movement of people, goods, and services.

But the agreement seems to be at risk. Why? The viability of the agreement is being called into question due to this year’s surge in migration from war-torn and economically-crippled countries in Africa and the Middle East, such as Eritrea, Syria, and Iraq. Under the separate Dublin Convention, anyone seeking asylum in Europe must register in the first country they enter. But many of the hundreds of thousands of migrants reaching Europe have been taking advantage of the Schengen zone’s lack of border controls to travel en masse to countries where they believe they have a better chance of gaining asylum and a better standard of living. This has led to widespread confusion and resentment building up amongst member states. Germany temporarily reintroduced border checks last month, with several other European countries following suit.

So what’s the solution? Germany wants European countries to agree to a common asylum seeker policy which would share the responsibility of refugees more equally. But other European states, such as non-Schengen member Britain, have said the only way to truly ensure the future of borderless travel in Europe is to focus on resolving the conflicts pushing people to migrate in the first place.