Michael Newton is the author of Age of Assassins.

It was a grey January day in St Petersburg in 1878 when Vera Zasulich, a young nihilist, made the short journey to the office of the city’s governor, General Fyodor Trepov. Here the general listened to petitions and examined complaints. A crowd of people had gathered in the cold. Zasulich waited in line for her turn to approach the great man. At last they spoke, and just as Trepov was turning from her to deal with the next supplicant, she pulled a gun from under her cloak and fired at him at point-blank range. The bullet burst into his pelvis, wounding but not killing him. Zasulich threw down the gun, stood quite still, and waited to be arrested. They beat her, of course, and then bundled her into a room, and then wondered a little feebly what to do with her next.

As they deliberated in the immediate aftermath of her deed, Zasulich moved from moments of dissociation and strangeness to an honest desire to offer advice to her baffled captors. Her words are quoted in a collection of revolutionary-era Russian memoirs, Five Sisters: Women Against the Tsar, edited by Barbara Alpern Engel and Clifford N Rosenthal:

My foresight, and consequently my precise plan of action, did not extend beyond the moment of attack. But every minute my joy increased – not because I was in full control of myself . . . but rather because I found myself in an extraordinary state of the most complete invulnerability, such as I had never before experienced. Nothing at all could confuse me, annoy me, or tire me. Whatever was being thought up by those men, at that time conversing animatedly in another corner of the room, I would regard them calmly, from a distance they could not cross.

This mingled feeling of elation and satisfaction appears often in the personal accounts of assassins; the work has been done and, in the process, their own lives thrown away. A sudden liberation from the burden of self fills them; they ascend to a height above life. They have realised themselves in the perfection of a deed.

Zasulich’s act succeeded by virtue of its comparative failure. Her shooting of Trepov was an act of revenge, after he had ordered an innocent man to be badly whipped in the house of detention on account of a small act of insubordination. Put on trial for her retaliation, she found herself acquitted unexpectedly; indignation against Trepov and sympathy for Zasulich’s courage meant only one possible end to the trial, despite the weight of evidence against her. That she had only wounded her man no doubt also facilitated her acquittal.

At the end of the trial, there were wild scenes of jubilation in court. Almost everyone was elated; only the judge and Zasulich were suitably sober. The result depressed the judge, who knew that it made a nonsense of the law, and disheartened Zasulich, who had been deprived of her death. She was confronted by the terrible responsibility of living on; freedom had been returned to her.

Zasulich’s state of mind following her attempt at murder is symptomatic of the "archetypal assassin" from the French Revolution onwards, that is, the assassin who struck at a prominent political figure for idealistic and ideological reasons. It illustrates how the results of assassination were perhaps always less vital to the perpetrators than the sheer exhilaration and abandonment central to the deed. There is no question that they also looked for a kind of political "success" in such murders, but in fact such triumphs were always more limited and less vital than the psychological rewards: the desire, in a righteous deed, to justify the self and in the same instant to escape its trammels.

It is doubtful how far assassinations have worked as an instrument of political or revolutionary change. In most cases, such murders have made only a negligible impression on events; the chaos and instability they carry with them have nearly always meant more than the change brought about by the deed.

One of the Great Courses, those DVD lecture series advertised in the New York Review of Books or the LRB, is on Events That Changed History. Two of its 36 defining moments are assassinations – the murder of Archduke Franz Ferdinand in Sarajevo in 1914 and the killing of John F Kennedy in Dallas in 1963. Both events look world-changing, but were they?..