The Islamic calendar contains two small letters which are a bit like the letters BC or AD or CE in the Gregorian calendar. These letters are "A.H" and they stand for the year of the hijrah. All of Islamic time is measured that way and to a strict Muslim this year is 1436 AH [until mid-October] and then 1437 AH thereafter. Now all of this sounds a bit trivial, but it is loaded with meaning.

A bit of history:

In 622 AD, Muhammad and his band of followers who did not have much of any political power moved to a city called Yathrib [now renamed Medina, which in Arabic means the city of the prophet]. Yathrib had a thriving Jewish population who were quite well off. Muhammad moved from his tribe's city of Mecca because he was not accepted in his role as a prophet or leader. In Medina he gained power by multiple methods, some of which changed over time. These included:

Convincing people of Medina to follow him due to his charismatic leadership.
Convincing other people of Mecca to come over an join him.
Convincing some Jewish people to join him.

In a fashion, this was still the non-compulsion stage of expanding his influence. Quickly, however, he realized that strategic alliances, force, and subjugation could achieve his goal of political and religious power much more quickly. This became the compulsion stage of his career and his methods included:

Expropriation of property.
Forced conversions.
Religious and political domination of all other groups.
Expulsion of those who did not agree with him.

Islamic history is thus dated from the time of the immigration to Medina as it marks the turning point in Islamic history from being in an oppressed minority situation to becoming the majority in terms of religious, political, and military power. This pattern has repeated itself throughout history.

Fast forward to today

The Islamic doctrine of hijrah or conquest via immigration is alive and well. In a similar fashion to the movement to Medina, the purpose is to first establish a beach-head, and then slowly gain increasing influence and power, likely in a peaceful way at first, and then more violent later. The goal, as it was in Medina, is not to cooperate and to assimilate to the local customs and culture—although that can be done for a short time in order to gain a critical mass of Muslims—but it is to strategically take over more an more areas of religious and political influence. Recall that the Albanian leader of ISIS said (quoting the example of Abraham from Sura 60:3), "We say to you as Ibrahim said to his father: "Verily we are free from you and whatever you worship besides Allah. We have rejected you, and there has started between us and you hostility and hatred forever, until you believe in Allah alone." If one looks at areas of London, Amsterdam, Paris and Stockholm, this replay of Islamic history is patently obvious. At present four hijrah tactics are being used to gain control of certain areas:

Multiplication of Muslims by birth rates
Multiplication of Muslims by immigration
Multiplication of Muslim influence via political systems
Expulsion of non-Muslims from certain areas by numerical and sometimes dominance by force—[think of the effect of documented rape-gangs in areas of Great Britain]

So what does this have to do with refugees?

ISIS has gone on record that it will swamp Europe with refugees. It is doing so and is simply using the playbook of Muhammad at Medina as very consistently ISIS is living out the adage "What Did Muhammad Do?" If we had a chance to replay history or to re-write history, the Jews of Medina who either were forced to convert to Islam, turned into sex slaves, killed or expelled, might have second thoughts about welcoming the "poor and oppressed and weak" band of followers of Muhammad and him as their leader. It would appear that non-Muslim countries today would need a great deal of discernment as to who is truly "poor and oppressed and weak" and whether or not they have any other agendas.