The attacks in Paris marked a new style of attack in which perpetrators used an amalgamation of two tactics: Gun attacks and suicide bombings, according to Haras Rafiq, managing director of the Quilliam Foundation, a counter-extremism think thank.

European governments have scrambled to increase security, particularly over the past two years in response to the rise of Islamic State and its ability to attract young Westerners. Measures have included strengthening counter-terror laws, enhancing intelligence-gathering capabilities and working to combat Islamist propaganda. Last year, European interior ministers agreed to tighten border checks on people entering the bloc as concerns mounted that airstrikes by Western governments in Syria and Iraq could encourage Europeans fighting there to return to their home countries…

The commando-style attack in Mumbai in 2008, which killed more than 160 people, drove home a whole new threat: that of armed individuals opening fire in public. Some European countries, including Germany and the U.K., stepped up their security measures after warnings of possible commando-style attacks in Europe. Some countries have also moved to put together a central domestic weapons registry that police can access quickly and are investing in more powerful assault rifles and training.