In late 2014, with the war in Syria approaching its fourth year and Islamic State making gains in the north of the country, the exodus of Syrians intensified. At the same time, others were fleeing violence and poverty in countries such as Iraq, Afghanistan, Eritrea, Somalia, Niger and Kosovo.

Vast numbers of Syrian refugees had been gathering in border-town camps in neighboring Turkey, Lebanon and Jordan since 2011. By 2015, with the camps full to bursting and residents often unable to find work or educate their children, more and more people decided to seek asylum further afield.

In 2015 an estimated 1.5 million people made their way on foot from Greece towards western Europe via the "Balkan route". The Schengen Agreement, which allows passport-free travel within much of the EU, was called into question as refugees headed towards the wealthier European nations.

Tens of thousands of refugees were also attempting the perilous journey across the Mediterranean on overcrowded boats. In April 2015, 800 people of various nationalities drowned when a boat traveling from Libya capsized off the Italian coast. This was to be just one of many similar tragedies - by the end of the year, nearly 4,000 refugees were reported to have died attempting the crossing.

Countries along the EU's external border struggled to cope with the sheer number of arrivals. Fences were erected in Hungary, Slovenia, Macedonia and Austria. Asylum laws were tightened and several Schengen area countries introduced temporary border controls.

Critics of German Chancellor Angela Merkel's "open-door" refugee policy claimed it had made the situation worse by encouraging more people to embark on the dangerous journey to Europe. By September 2016, Germany had also introduced temporary checks on its border with Austria.

In early 2016, the EU and Turkey signed an agreement under which refugees arriving in Greece could be sent back to Turkey. The deal has been criticized by human rights groups and came under new strain following a vote by the European Parliament in November to freeze talks on Turkey's potential accession to the EU.

With anti-immigration sentiment in Europe growing, governments are still struggling to reach a consensus on how to handle the continuing refugee crisis. Attempts to introduce quotas for the distribution of refugees among EU member states have largely failed. Conflicts in the Middle East and elsewhere show no signs coming to an end, and the death toll from refugee sea crossings is on the rise.

Police in Leipzig arrested 22-year-old Syrian refugee Jaber al-Bakr after a two-day manhunt following the discovery of explosives and other bomb-making equipment at his apartment in Chemnitz. He was suspected of plotting to attack a Berlin airport. Two days later, he hanged himself in his prison cell.

In July, the "Islamic State" (IS) claimed responsibility for two attacks carried out by asylum seekers. 15 people were injured in a crowded wine bar next to the entrance to a music festival in the Bavarian town of Ansbach after a rejected Syrian asylum seeker detonated an explosive device. The man killed himself in the attack.

A 17-year-old asylum seeker wielding an axe and a knife went on a rampage on a regional train near Würzburg, seriously injuring four members of a tourist family from Hong Kong and a passer-by. The attacker was shot dead by police. German authorities said the teenager was believed to be a "lone wolf" inspired by the IS, but without being a member of the network.

Three suspected members of the "Islamic State" terror network were arrested in the German states of North Rhine-Westphalia, Brandenburg and Baden Württemberg. Authorities say two of the men planned to blow themselves up in downtown Düsseldorf, while the other attacker and a fourth jihadist arrested in France planned to target pedestrians with guns and explosive devices.

Police arrested three people over a bomb blast that injured three people in a Sikh temple in Essen. The bomb detonated after a wedding party, blowing out windows and destroying a part of the building's exterior. A 16-year-old suspect turned himself in after police showed footage of the attack from a surveillance camera and special police units arrested another young suspect in his parents' home.

German-Moroccan Safia S. is charged with stabbing a police officer at the main train station in the northern city of Hanover. The 16-year-old girl is suspected of having been "motivated by members of the Islamic State group in Syria to commit this act," chief prosecutor Simon Heinrichs said.

In separate raids across the country, police arrested three Algerians suspected of links to the "Islamic State" militant group and of having planned a terrorist attack in Berlin. The Berlin prosecutor's office said prosecutors were aware of a "concrete" plan to target the capital.

The Eschborn-Frankfurt City loop bike race was called off after German police discovered it may have been the target of an Islamist terror attack. A 35-year-old German with a Turkish background and his 34-year-old wife were arrested on suspicion of planning the attack. Police found bomb-making materials in their home near the bike route.