Few read history, fewer still remember it, and all but a few fail to learn and remember the LESSONS of history. History is really our best laboratory for discerning cause and effect, what happens when you do X and what when you do Y, in circumstance Z.
We know, for example, that the best of intentions can and often have led to disastrous outcomes.
In 1948, the UN declared Israel a nation. Immediately every neighbor they had invaded. Syria, Lebanon, Jordan and Egypt all sent their armies in to crush the Israelis–contrary to international law and intention, to be clear.
In what can only be called a miracle, one born of the desperation of having just had 6 million members of their “tribe”, I will call it, slaughtered–in perhaps not the largest mass murder in history, which is filled with them, but certainly the first to apply modern science to the process–the Jews prevailed.
This war created many refugees. Some, but not all, Muslim Arabs left the nation. Those who stayed remain citizens of Israel, with more guaranteed rights than are afforded any other comparable group of Arabs living in largely Arab nations. They have more rights, say, than they would in Saudi Arabia, or Egypt, or Tunisia, or Algeria. This, despite the fact that some rights are still denied them.
Most of the refugees, if I recall correctly, went to Jordan. They caused trouble, and many if not most got kicked out. Then they went to Lebanon, and caused trouble there, too. Eventually, they were given effective control of the West Bank–formerly a part of Jordan, and captured in a war with that nation–and the Gaza Strip, itself also taken in war with Egypt.
Many of them, 67 years later, still live is these refugee camps. Nobody wants them because they cause trouble, and everyone in the Arab world knows this. If they wanted peace with Israel, all they would to do is honestly lie down their weapons. They refuse to do this, despite the impossibility of a military victory of any sort.
It seems to me that many European nations are likely indulging in a fatal kindness. These groups, in the numbers they are emigrating, are well positioned to cause major problems, likely beginning nearly immediately, and that is the case even before you factor in that ISIS has already SAID that it fully intends to use this crisis to foment and commit acts of violence against virtually all of humanity.