His father had moved into a suburban villa there with August Bebel after they were expelled from Leipzig under the 'Lesser State of Siege', a provision of the Anti-Socialist Laws directed against socialist, social democratic and communist associations and writings.

Anti-militarist agitation, he said, must educate about the dangers of militarism, but it must do so within the framework of the law – a statement that the Reich Court of Justice did not accept when Liebknecht was brought to trial for treason.

The treason trial against Liebknecht took place before the Reich Court of Justice, presided over by Judge Ludwig Treplin, on 9, 10 and 12 October 1907, with a large public presence.

He was also able to prove that the Krupp company, a large steel and armaments firm, had illegally obtained economically important information by bribing employees of the War Ministry (the so-called Kornwalzer scandal).

[16] In the party's preparatory meeting on 3 August, there were, according to SPD representative Wolfgang Heine, "vile, noisy scenes"[17] because Liebknecht and 13 other deputies spoke out decisively against war loans.

In the 4 August parliamentary session, however, the Social Democratic faction voted unanimously in favor of approving the loans that enabled the government to finance the initial war effort.

The importance of the credit approval in the shift of the faction's entire policy to the government camp was not obvious: there was still the hope that the decision of 3 August was the result of a temporary panic and would soon be corrected, or at least not repeated and even overridden.

"[20] Liebknecht expressly did not endorse a statement by Rosa Luxemburg and Franz Mehring (its complete text is thought to have been lost),[21] in which they threatened to leave the party because of its conduct.

Liebknecht's first major conflict with the new party line, one which attracted wide public attention, came when he traveled to Belgium between 4 and 12 September, in the middle of the 3-month long German invasion of the country.

There he met with local socialists and was informed – in Liège and Andenne, among other places – about the mass reprisals ordered by the German military against alleged attacks by Belgian civilians.

[22] After that he was all the more determined to vote against the new loan bill and to make it a demonstrative statement against the "unity phase's high tide"[23] and for it to be the basis for rallying opponents of the war.

Liebknecht was in the end the only deputy not to stand when Reichstag President Johannes Kaempf called on the House to approve the supplementary budget by rising from their seats.

Contrary to customary practice, the Reichstag president did not record in the official minutes the statement that Liebknecht had submitted in writing explaining his vote against the second war loan bill on 2 December 1914.

In April 1917 the SPD split apart with the founding of the Independent Social Democratic Party of Germany (USPD), which the Spartacus group joined in order to work within it toward revolutionary goals.

In some cases support was even publicly justified on the grounds of Germany's strategic interests and the alleged existential threat to Turkey from Armenian and Arab terrorism.

Liebknecht was released from prison on 23 October 1918 as part of a general amnesty that the Reich government hoped would act as a relief valve for the pre-revolutionary mood in the country.

He urged the Revolutionary Stewards, which had organized the January strike, and both the USPD's rank and file and the Spartacus League to jointly coordinate preparations for a nationwide revolution.

The Stewards, guided by workers' sentiment in the factories and fearing an armed confrontation with army troops, postponed the date set for the revolution several times, finally to 11 November 1918.

In order to push the November Revolution in the direction of a socialist soviet republic, he and Rosa Luxemburg began publishing a daily newspaper, Die Rote Fahne ('The Red Flag').

Beginning on 8 January, Liebknecht and other KPD members participated in the Spartacist uprising which began with a general strike and the occupation of several Berlin newspaper buildings.

[35] In December 1918 numerous red, large-format posters directed against the Spartacus League were posted in Berlin, culminating in the demand "Beat their leaders to death!

Rumors circulated among civilians and military personnel – spread by, among others, Philipp Scheidemann's son-in-law Fritz Henck – that bounties had been placed on the Spartacist leaders.

[42] The owner of the apartment, the merchant Siegfried Marcusson, was a member of the USPD and belonged to the Wilmersdorf Workers' and Soldiers' Council; his wife was a friend of Rosa Luxemburg.

In the early evening of 15 January, five members of the Wilmersdorf Bürgerwehr – a middle class civilian militia – entered the apartment and arrested Liebknecht and Luxemburg.

From there a member of the Bürgerwehr called the Reich Chancellery and informed its deputy press chief, Robert Breuer of the Wilmersdorf SPD, that Liebknecht had been captured.

[53] Also present were Captain Heinz von Pflugk-Harttung, Horst's younger brother; Second Lieutenant Bruno Schulze; and Private Clemens Friedrich, the only enlisted man involved in the crime.

Half an hour later, Luxemburg was taken away in an open car and shot about 40 meters from the entrance to the Eden Hotel, apparently by Naval Lieutenant Hermann Souchon.

Pabst's press officer Friedrich Grabowski subsequently circulated a communiqué stating that Liebknecht had been "shot while fleeing" and Luxemburg "killed by a mob".

The military court prosecutor Paul Jorns impeded the investigations, and in the main trial only Otto Runge and Kurt Vogel were sentenced to prison terms.

[64] The annual Liebknecht-Luxemburg commemorations in Berlin marking the anniversary of their murders on the second Sunday in January are attended by a wide range of left-leaning groups, parties and individuals.