Al-Qaida propagandists have long incited sympathisers to strike local, familiar targets using any available means. Post-9/11 obstacles to al-QaidaвЂ™s preferred strategy of symbolic вЂspectacularвЂ™ attacks in top tier Western cities devolved much responsibility to homegrown, lone wolf extremists by the late 2000s. Terrorist groups strive to take advantage of gaps вЂ“ for example, by cultivating safe havens and staging grounds in the anonymous urban sprawl вЂ“ and exploit social divisions to radicalise sympathisers. Concurrently, the resulting close proximity of disparate ethnic, religious, linguistic and economic groups has been seen in some instances to result in social divisions. Rapid, often unplanned city growth leaves glaring gaps in public service provision, including law enforcement. The speed of urbanisation over the last few decades, especially in emerging and developing countries, has also shaped the threat environment. The attractiveness of cities to terrorists will only increase: since 2007, more people live in urban than rural areas for the first time in human history by 2050, the estimate is that 75% of global population will be urban. Put another way, population density and urban complexity multiply the desired physical, psychological and strategic impacts of terrorism. Urban systems such as mass transit also rapidly transmit the disruptive effects of terrorism citywide. (Also, leftist terrorism associated with agrarian peasant insurgencies has largely subsided outside of South Asia.) In cities, more people are directly or indirectly exposed to individual terrorist acts, and the concentration of interest ensures publicity and attention.

Terrorist groups target cities because they are centres of political power and population. Baghdad, Cairo, Islamabad, Mumbai, Buenos Aires, Beirut, Jerusalem, Paris, Jakarta, Los Angeles, Nairobi: regrettably few major urban areas are unfamiliar with major terrorist attacks. The most lethal terrorist attacks in history on 11 September 2001 symbolically targeted the financial and political centres of the US. Previous waves of terrorist activity, such as decades-long campaigns by the Irish Republican Army (IRA) in London and Euskadi Ta Askatasuna (ETA) in Madrid, consistently targeted capital cities.

Urban terrorism is not new, or even the вЂnew normalвЂ™.

List of normal urban terror maps