6. How has Europe responded?
Tensions in the EU have been rising because of the disproportionate burden faced by some countries, particularly the countries where the majority of migrants have been arriving: Greece, Italy and Hungary.
In September, EU ministers voted by a majority to relocate 160,000 refugees EU-wide, but for now the plan will only apply to those who are in Italy and Greece.
Another 54,000 were to be moved from Hungary, but the Hungarian government rejected this plan and will instead receive more migrants from Italy and Greece as part of the relocation scheme.
The UK has opted out of any plans for a quota system but, according to Home Office figures, 1,000 Syrian refugees were resettled under the Vulnerable Persons Relocation scheme in 2015. Prime Minister David Cameron has said the UK will accept up to 20,000 refugees from Syria over the next five years.