Modern terrorism can be traced back to nineteenth century revolutionary radicalism, and, in particular, the emergence of "anarchist", "collectivist anarchist" and "anarcho-communist" groups. For example, from the mid-nineteenth century onwards, groups led or influenced by the Frenchman Pierre-Joseph Proudhon, author of What is Property? (1840), the German Karl Marx, and the Russian Mikhail Bakunin, were promoting one or another anti-establishment model. Within a decade, similar groups had appeared throughout Western Europe, the Balkans and Asia. The German revolutionary Karl Heinzen was the first to articulate the use of violence, even mass murder, by individuals to effect political change in his influential 1853 pamphlet, Mord und Freiheit, coining the term Freiheitskämpfer or "freedom fighter" in the process. However, as these early radicals became disillusioned by their failure to provoke widespread social revolution among the peasantry through traditional means such as distributing political pamphlets and leaflets urging uprisings and riots to put government under pressure, they turned instead to violence in the hope of forcing political reform and of undermining the State. In this way, "propaganda by the deed", as a strategy for political action, became central to the politics of European anarchism (see for example, Fleming, 1980).
The principal violent method of spreading terror utilized by virtually all such groups at the time was targeted assassination, which not only carried with it serious personal risk but also the potential for political martyrdom. The assassination of Czar Alexander II in 1881 by the Russian revolutionary group Narodnaya Volya is emblematic of this period of terrorism. Targeted assassination could be differentiated from ordinary criminal acts, because targeting persons acting in an official State capacity signified a deep, personal commitment to a "cause that could inspire others, and epitomised the revolutionary 'code of honour' by sparing innocent citizens". This arguably made terrorist assassination a more humane form of violence than civil war, since the terrorist's targeted attack would strike only against State "oppressors", and would help maintain the low casualty rate of terrorism that was also an advantage of the "propaganda by the deed" strategy (Morozov, 1880, p. 106).
Technological developments in the mid and late nineteenth century also played a pivotal role in the rise of terrorism. The ready availability of dynamite allowed terrorists to perpetrate and disseminate their deadly acts more widely as propaganda by the deed. The development of mass communication technologies allowed news, learning, ideas and events to be rapidly communicated across long distances, opening up an era of mass communication and of migration that was crucial to inspiring groups elsewhere. The invention of the telegraph and the steam-powered rotary press meant that newspapers could receive messages almost instantly after transmission from around the world and gave millions of people access to information about events virtually as soon as they occurred. New technologies, together with greater access to educational opportunities, facilitated the migration of agricultural labourers and artisans to urban centres. The development of commercial railways and trans-Atlantic passage steamers aided groups to travel long distances, and to carry their political sympathies further afield.
Although the successful assassination of Czar Alexander II would initially inspire a wave of anarchist violence that shook Europe and the Americas over the following decades (Zimmer, 2009), Russian rebels encouraged and trained a variety of rebel groups who were emerging elsewhere, even when their political aims were vastly different. While a narchists carried out bombings in France, Germany, Italy, Spain and elsewhere, which at times turned into cycles of retribution between anarchists and the authorities (Zimmer, 2009), Western States attempted to stem the tide through such legal mechanisms as immigration controls and extradition treaties targeted against "undesirable aliens". These included a protocol concerning measures to be taken against the anarchist movement, signed on behalf of nine States in March 1904, and an administrative convention for the exchange of information concerning individuals considered dangerous to society, signed in October 1905 (Hudson, 1941, p. 862). By the mid-nineteenth century, many extradition treaties exempted fugitives accused of "political offences" or "crimes of a political character" from extradition (Hannay, 1988, p. 116). Only the conservative regimes of Austria, Prussia, Russia, and Naples persisted in advocating that ideologically similar nations should use their extradition laws to help suppress each other's revolutionaries (Pyle, 1988, pp. 181-182).
On 28 June 1914, Gavrilo Princip, a young Serbian nationalist and supporter of the clandestine Black Hand group, which wished to bring about a Greater Serbia, assassinated the Archduke of Austria and heir presumptive, Franz Ferdinand, and his wife, in Sarajevo. This event unleashed a "domino effect" of defensive alliances developed in the pre-war years, leading to the "total war" of World War I, which irrevocably changed the face of terrorism for the eras to come. By the end of the war, with the return of fully-trained soldiers to their homes and families, the tactics and methods learned in "total war" between 1914 and1918 would continue to haunt States. As revolutionary politics at the local level continued to simmer throughout the nineteenth century, the continued availability and use of "political offence" exceptions as grounds upon which States might refuse requests by other States for the extradition of persons suspected of having perpetrated violent offences for various ideological, religious or political motives highlighted the difficulties associated with distinguishing criminal acts of terrorism from criminal acts generally. These definitional issues have continued to the present day.