Depending upon when you read this article, you can fill in the blank. As I write, the newest was in Barcelona, Spain, perpetrated (so officials think) by an ISIS-inspired Moroccan, 18-year-old Moussa Oukabir. According to reports, Oukabir had recently "joked" on social media, when asked what he might do on his first day as absolute ruler of the world, "Kill all infidels and only allow Muslims to continue the religion."
That we hope each attack will be the last, as if we're merely weathering a passing storm, attests to our general ignorance of deep history — history stretching back far beyond the latest news.
To correct that ignorance, we should go back to the beginnings of Islam in the 600s to find out what an 'infidel' is, and why he should be killed.
Many are not aware that the great source of radical Islamic hatred towards "infidels" is the result of its acceptance of parts of the Bible: the Torah (the first five books of the Old Testament), the Psalms, and a significantly different version of the Gospels, all of which, the Koran attests, point to Muhammad as the prophet. According to the Muslim understanding, Moses, David, and Jesus all proclaimed the truth finally revealed to Muhammad and written down in the Koran.
But Jews and Christians turned away from that truth, and are therefore worse than pagans and other unbelievers, for they had the truth and rejected it. They are "infidels" (kafirs) and marked out for death, for they have fallen away from the true religion, Islam. Christians in particular are bad because they rejected the truth of Islam and they deified Jesus, committing the only unforgivable sin in Islam, shirk, the deification of anyone other than Allah.
Infidels stand in the way of the universal acceptance of Islam. As the Koran states (9.29), "Fight those who do not believe in Allah or in the Last Day and who do not consider unlawful what Allah and His Messenger have made unlawful and who do not adopt the religion of truth from those who were given the Scripture," i.e., the Koran.
Christianized Europe has therefore always been a target for takeover by Islam. Spain had been conquered by the early 700s, about a hundred years after the death of Muhammad, but was slowly re-Christianized over the next 800 years. The recent attack in Barcelona, Spain is — in the larger view of history — understood by Islamic radicals as a retaking from the infidel of what is rightfully theirs.
It isn't just Spain that radical Islam desires to retake, but all of Europe. To understand this aspect of deep history, we may go back 500 years, to the time of the Reformation.
In the century prior to Martin Luther's famous challenge to reform in 1517, Islam had advanced in a kind of pincer movement, the Islamic caliphate of the Ottomans taking over Constantinople in 1453, thereby directly threatening Europe. It was no idle threat. Within decades, Greece, Serbia, and the Balkan territories south of the Danube were conquered, then the Levant and Egypt, Iraq, North Africa, most of Hungary, and even part of southern Italy. In 1529 the Ottomans were knocking at the gates of Vienna.
That is the historical moment which radical Islam now seeks to revive, the time when it seemed as if infidel Christian Europe would finally be won by Islam at the height of its power.
The justified fear of Europeans today about radical Islam is therefore nothing new. Christian Europe 500 years ago felt that very same fear, and both Catholics and Protestants believed that they were living in the end times. (Interestingly enough, part of the reason Luther was able to gain traction in Germany was that the energies of Catholic Emperor Charles V were focused almost entirely on keeping the Muslim advance at bay.)
Yet, there are differences between then and now. The most important is that Europe has now largely been de-Christianized because of the cultural and political advance of radical secularism (an advance, as I show in The Reformation 500 Years Later, which began in the 1400s).
Radical secularism today has great difficulty in understanding the threat of Islam — and therefore even greater difficulties in dealing with it — because it has for centuries cherished the assumption that all religions are equal (as in, equally false), but Christianity is the worst among equals and (ironically) Islam the best.
That long-standing attitude accounts for the curious situation today where secular European states regularly persecute Christianity as an enemy to civilization even while cheerfully waving in radical Muslims who are actively trying to destroy it.