AS EUROPEANS know to their lamentable cost, assassinations can start wars, even world wars. A bullet fired by a Serbian nationalist, killing Austria’s archduke in June 1914, sparked the calamitous first world war which arguably paved the way to the second. Earlier assassinations may have drastically altered the course of history, too. The bomb thrown in 1881 at Tsar Alexander II, who had emancipated the serfs, woefully stymied reform in Russia.

More recently, the murder in 1961 of Patrice Lumumba, the Congolese prime minister, often blamed on the CIA, helped set that country on its path to mayhem. The killing in 1994 of Rwanda’s president, Juvénal Habyarimana, set off Africa’s worst genocide. The murder of Israel’s prime minister, Yitzhak Rabin, by a Jewish fanatic the following year dimmed the prospect of peace between Israelis and Palestinians. The assassination in 2007 of Benazir Bhutto, when she was bidding to become Pakistan’s prime minister, stalled her country’s efforts to build democracy.

These and other cases suggest that Benjamin Disraeli was wrong when, after Abraham Lincoln’s killing, he remarked, “Assassination has never changed the history of the world.” And given its frequency, it would be stranger if it did not. From 1875-2004, 298 assassination attempts on national leaders were reported, according to a paper by Benjamin Jones and Benjamin Olken published by Northwestern University in America in 2007. They count 59 resulting in a leader’s death. Since 1950 a national leader has been assassinated in nearly two out of every three years.

Yet an attack does not have to be on a head of state to prove a political shock. The phenomenon of state-sanctioned attacks on perceived enemies at home, but especially abroad, has recently concentrated the minds of lawyers and policymakers. The neurochemical attack this month on Sergei Skripal, a retired Russian double agent, in Salisbury, a sleepy British cathedral city, is just the latest in a line of brazen incidents. On March 12th Britain’s prime minister, Theresa May, told Parliament that the Russian state was “highly likely” to have been the perpetrator. Two days later she announced the expulsion of 23 Russian diplomats (see article).

If Mrs May is right, the attack in Salisbury would join the list of attempts by the Russian state under Vladimir Putin to kill its enemies. On his own turf journalists, politicians and businessmen have been murdered. But the assassination of enemies on the soil of other countries is more audacious. Russia’s successor to the KGB, the Federal Security Service (FSB), sometimes in cahoots with criminal business networks that have thrived under Mr Putin, has not hesitated to kill perceived enemies of the state abroad, such as Alexander Litvinenko in London in 2006. The targeting of Mr Skripal—presuming he was a victim of the FSB—is not all that unusual.

And Russia is far from the first country to seek out and kill supposed enemies abroad. During the Cold War, military regimes in South America co-operated to kidnap and murder leftists who had sought exile in countries outside their own. Under apartheid, the South African government assassinated members of the now ruling African National Congress in neighbouring countries.

Licences to kill

The state that over the past half-century has most actively pursued a policy of hunting down and killing enemies abroad is surely Israel. According to Ronen Bergman, a prominent Israeli journalist, whose history of the subject, “Rise and Kill First”, was published this year, Israel’s security services have carried out some 2,700 assassinations. After Palestinians began to target Israelis across Europe, notoriously killing 11 members of the Israeli Olympic team in Munich in 1972, Mossad, the Israeli security service, was given a free rein to hunt down such enemies (though Mr Bergman questions whether the Munich attackers were ever killed). From then on, a string of attacks on Palestinian operatives in such places as Jordan, Lebanon, Malta, Tunisia and the United Arab Emirates was carried out.

Assassinations of Palestinians suspected of planning or perpetrating violence against Israelis have been relentlessly conducted also in the West Bank and Gaza, territories controlled by Israel that seek to become an independent Palestinian state. Khaled Meshal, who went on to become leader of Hamas, a Palestinian Islamist group that has carried out myriad suicide attacks, narrowly survived after being poisoned in the ear in Amman, Jordan’s capital, in 1997. Sheikh Ahmed Yassin and Abdel Aziz al-Rantisi, successive leaders of Hamas, were both assassinated by Israel in 2004. According to Mr Bergman, the Israelis assassinated more than 300 Palestinians (and 150-odd bystanders) during the intifada (uprising) of 2000-2005.

What the Israelis have termed “targeted preventions” by snipers, booby-traps, helicopters, F-16 fighter jets and increasingly by armed drones were at first often criticised by Western governments for violating international and humanitarian law. But after Osama bin Laden’s attack on the Twin Towers on September 11th 2001, the American administrations of George W. Bush and then Barack Obama, and more recently the British and French governments, have in some respects followed the example of the Israelis in tracking down and killing enemies abroad, sometimes including their own citizens, by using drones.

A year ago President Donald Trump approved a Pentagon request to designate parts of three unnamed Yemeni provinces as “areas of active hostilities” where suspected enemy fighters could be targeted. The term has no clear legal definition, says Peter Bergen of New America, a think-tank. But it lets armed forces operate as they do in conventional war zones and hit terrorist targets at will. The Trump administration has expanded the area where American forces conduct drone strikes from Pakistan, Yemen and Somalia to include Niger.

Whereas attacks such as the one on Mr Skripal have been almost universally condemned, the use of drones to kill targeted individuals has been more contentious. Many human-rights lawyers see them as unlawful. Agnes Callamard, the UN’s special rapporteur on extrajudicial, summary or arbitrary executions, says that “outside the context of active hostilities, the use of drones for targeted killing is almost never likely to be legal,” adding that lethal force can only be legally used when there is evidence that it would protect against an imminent threat. She also deplores the “kill lists” of what the Americans call “specially designated global terrorists” who, she says, have no way of proving that they are not, for example, helping al-Qaeda, yet in effect face a sentence of death without due process of law.

The Israeli and American authorities dislike the word “assassination” being applied to what they prefer to call “targeted attacks” because it implies a flouting of international law. At the end of 2016, just before he left office, Barack Obama issued a report on the legal framework guiding the United States’ use of force. It says, “Using targeted lethal force against an enemy consistent with the law of armed conflict does not constitute an ‘assassination’.” Assassinations, it notes, are unlawful under an executive order signed by Ronald Reagan in 1981 (which updated those by Gerald Ford and Jimmy Carter). But today there is “a new and different kind of conflict against enemies who do not wear uniforms or respect geographic boundaries and who disregard the legal principles of warfare.”

Broadening the battlefield

By implication this requires more elastic rules to be followed by governments facing such challenges, while broadly invoking the principle of self-defence to apply to enemies in the territory of another state. Due process, it is argued, cannot be applied when responding to an imminent attack or when the capture or extradition of a suspected enemy is not feasible. The report by the Obama administration also notes that it is permissible to “impinge on another state’s sovereignty” if it is unable or unwilling to “mitigate the threat emanating” from its own territory. Witness the case of Pakistan and bin Laden, subjected to a “targeted killing” in 2011.

Those on either side of the debate continue to argue over definitions of “self-defence”, “active hostilities” and “imminent”. For their part the Israelis also posit a “ticking bomb” argument: even if an attack is not imminent, a would-be perpetrator is still a legitimate target, they argue, because he is bent on an eventual attack. Amnesty International, by contrast, has denounced a “policy of assassinating those who do not pose an imminent threat to lives”. It is, says the human-rights organisation, “unlawful and should be stopped.” The Israelis have also been criticised for disproportionality, particularly regarding the deaths of bystanders. When in 2002 another Hamas leader, Salah Shehadeh, was killed by a one-tonne bomb dropped on his house, 16 civilians, including nine children, were also killed, according to a report by Amnesty International.

Philippe Sands, a lawyer who has charged both the American and British governments with violations of the laws of war, writes: “It’s a series of binaries. The first is whether a situation of armed conflict (war) exists. If it doesn’t, extrajudicial executions are a total no-no in all circumstances. If armed conflict exists, then every case turns on the facts.” The snag here, in the Israelis’ view, is that they are locked in what they call “an armed conflict short of war”, and that their survival as a nation cannot depend on the niceties of the law. Other scholars note that the norms around state-sanctioned killings have long shifted. Writing in 1516, Thomas More, the theologian-cum-politician, argued that assassination was a way of keeping ordinary citizens off the battlefield. But by 1789 Thomas Jefferson could write to James Madison that “assassination, poison, perjury” were “held in just horror in the 18th century”. In 1806, Britain’s foreign secretary not only blocked a plot to kill Napoleon but informed the French. Yet as the litany of assassinations in the 20th century suggests, its use as a weapon of war returned to popularity soon enough. But whether you call it assassination or targeted killing, is it effective? In the Russian case, the motive is mainly to instil fear into prominent people who dare to contest the current establishment and to punish traitors, whether they are no longer Russian citizens or reside abroad. Mr Putin, already widely considered a pariah in terms of international law, may think he has nothing to lose by arousing Western hostility still more. In Israel’s case it is to keep its enemies militarily on the back foot and force them into concessions, though it may conversely make them less minded to seek a lasting peace.

No end in sight

What is certain is that the practice of states killing prominent or particular individuals without recourse to the law will persist. Indeed, advances in toxicology and in the technology of drones may make it even more attractive as a weapon in the hands of governments who want to wage war without actually declaring it—and without sending armies across borders.