The assassination of Russia's ambassador to Turkey at roughly the same time that 12 Germans were apparently murdered in a Berlin truck attack has accentuated the air of inevitability now surrounding Islamist-inspired terrorist attacks in the West. Whereas years passed between the terrorist bombings of Madrid's train system in 2004 and London's underground in 2007, Europe's last major terrorist attack occurred in July, when a 19-tonne truck drove in Bastille Day crowds, killing 84 people. Lone-wolf attacks carried out either by Islamic State sympathisers or Muslims aggrieved by western meddling in the Middle East occur every other week, seemingly. And Germany, where such incidents had previously been rare or unknown, has endured many of them.
Ambassador Andrei Karlov's assassin revealed his anger at Russian military intervention in Syria in explicit terms, while the Berlin attacker (allegedly an asylum-seeker of Afghan or Pakistani origin) appears to have been inspired by IS's propaganda message to its followers to use trucks and other hard-to-counteract means to cause maximum carnage in order to sow the seeds of division in multicultural western societies.
IS is becoming increasingly isolated in its Syrian and Iraqi strongholds, which seems to offer some hope that the current cycle of violence will slow in intensity or number. On the other hand, the subculture of Islamic extremism – which is rooted in anti-western, anti-Semitic and homophobic sentiment – appears to be flourishing. The high incidence of European terrorist attacks carried out by second-generation Muslim family members attests to the fact.
Where militants and ideologues once argued that murder in defence of Islam was permissible, they now argue that it is obligatory, and indeed positively glorious. While moderate Muslims reject this ideology, it is nonetheless apparent that many appear to sympathise with the view that any disrespect towards Islam, say by the publication of satirical cartoons of the prophet Mohammad in a magazine like Charlie Hebdo, warrants severe punishment.
Ambassador Karlov's death will not see the Russian government rethink its Syrian involvement – Vladimir Putin's ambitions for Russia to be a major Middle Eastern power-broker will trump any annoyance he may have over Turkish security lapses in an Ankara art gallery, and terrorism has its uses in an authoritarian country like Russia.
Introspection and brooding in Germany after the Berlin attack looks assured, with Angela Merkel's reelection bid likely to suffer. Mrs Merkel's 2015 decision to allow a million Middle Eastern asylum-seekers to settle in Germany is still widely supported, and she herself has spoken forcefully about the need for asylum-seekers to integrate completely in their new homeland. But every new terrorist attacks threatens that consensus.
Previous cycles of terrorism in Europe have lasted, on average, about 15 years, with attacks generally diminishing in intensity as government and counter-terrorism agencies meet the new threats. This is religious-inspired terrorism, however, fed by under-educated, under-employed young men trapped on the fringes, and bets on its duration may be risky.