On Monday night, a suicide bomber struck an Ariana Grande concert in Manchester, England, killing 22 people and injuring dozens more. The terror group the Islamic State (commonly referred to as the Islamic State of Iraq and Syria, or ISIS) has claimed responsibility for the attack, and the United Kingdom is now at its highest terror alert level in 10 years. Many of the bomber’s victims were young, female fans in the audience. But this horrific attack didn't take place because Ariana Grande threw a concert. This attack happened because Ariana Grande happened to throw a concert in Manchester, England.

Manchester, a city with roughly half a million residents, is around 160 miles northwest of London, and part of a larger metropolitan region of about 2.5 million people. It is one of the most visited cities in England, which is, in turn, one of the world's largest and most important travel hubs and cultural and political power centers. It is also a nation that has experienced a number of serious and deadly terror attacks since the early 1990s, including the London Underground bombings in July of 2005 (in which 52 people were killed) and the murder of five people on and near Westminster Bridge (outside the British Houses of Parliament) just two months ago.

England's physical location puts it in relatively close proximity to countries experiencing surges of violent extremism, including ISIS strongholds in Syria and Iraq. The Manchester bomber is believed to have recently flown back and forth between Libya, where his parents lived, and the United Kingdom. More than 850 residents of the United Kingdom have traveled to the Middle East to join extremist groups. Many of those people died in combat, but some of those who joined ISIS and other jihadist groups returned home. Others never left. Some of these individuals went on to carry out public acts of violence intended to strike fear in Western countries, with relatively little communication with anyone on the ground in the Middle East.

European nations like France and Belgium have been frequently targeted by fundamentalist groups, whose acts were organized or inspired by ISIS or other radical Islamic organizations. The reasons the United Kingdom is frequently attacked are more complex, and involve, in part, Britain's colonial past in the Middle East (the borders of Iraq and Syria were co-constructed by an English aristocrat using a ruler on a map in 1916). Attacks in this century can likely be traced to the U.K.'s commitment to be an ally to the United States in the War on Terror. This year, the Royal Air Force and U.K. ground forces have taken part in the U.S.-led coalition fighting ISIS in Syria, and the RAF was responsible for dropping more than 200 bombs from January to April 2017, helping cost the terror group vast acres of territory and millions of dollars in the region.

In retaliation, ISIS has encouraged individuals or small groups already living in countries like France and the U.K. to attack civilians in large public gatherings — like concerts. In November 2015, 89 people were killed at an Eagles of Death Metal concert at the Bataclan theater in Paris, which turned out to be part of a coordinated attack on everyday Parisians that killed 130 people and wounded nearly 400 more.

Britain's history with terrorism has led the country to develop a legal framework for combating it that other nations might lack. Prior to 2005, the Irish Republican Army was responsible for multiple terror attacks, in reaction to British control of Northern Ireland. The frequency of those attacks, and the destruction they caused, has led the British government to be among the Western world's most aggressively proactive in working against terror and terrorism.

This approach continues today. In July of 2000, Parliament passed Terrorism Act 2000, giving the government sweeping permissions to act against any threat from a political, social, racial, or religious cause aimed at any section of the public. The act was controversial. One provision, repealed in 2011, gave the police the power to arrest anyone for potential terror activity without requiring their concerns to be "reasonable" (for example, one man was arrested on suspicion of terrorism for wearing a heavy jacket in July). But parts of Terrorism Act 2000 and subsequent acts passed in reaction to the 2005 London Underground bombing are still in effect. As of 2006, anyone can be held for up to 28 days without being charged with a crime if they are suspected of being a terrorist. And the British police have raided apartments and arrested dozens of terror suspects in the last year alone.

Despite these legal safeguards, some types of attacks are still hard to account for. For example, those involving a "lone wolf" — a person outside of a specific terror network committing violent acts independently — are notoriously difficult to prevent. These terrorists often use materials that are easy to get and even easier to conceal — like small knives or homemade bombs small enough to fit into a duffel bag, or, in the case of the Westminster Bridge attack, objects like a car. Even larger-scale attacks, like the terror attack in Nice, France, last July, can use commonly available objects to create death and destruction without drawing the initial attention of authorities. In Nice, a 19-ton cargo truck was driven into a crowd of people celebrating Bastille Day, killing more than 80 and wounding hundreds of others.

Two days after the attack in Manchester, we know the bomber's name. We don't know if he had help assembling the bomb or obtaining the materials he used, who (if anyone) directed his actions, or whether there are any more attacks in the making. On Wednesday, the BBC reported that at least one official believed the bomber to be a "mule," carrying a bomb made by someone else. Investigators in the United Kingdom and in Europe are continuing to examine evidence and review the bomber's past in detail.

Ultimately, this bombing did not take place because of an Ariana Grande concert, but was part of something much bigger: an attempt to terrorize everyday people, like young girls going to their first concert, older teens wanting to celebrate with their friends, and young people who just wanted to enjoy a night out. Twenty-two people, including small children, were murdered to send a message to the British government and to the British people: You're not safe here.