Syndicalists viewed class interests as irreconcilable and advocating overthrowing capitalism and replacing it with workers' collectivized control of industry.

[2] In 1909, the NAS declared: "To us it appears [...] necessary that the question of whether the isolation of revolutionary organizations is to be perpetuated should be posed seriously in every country"[3] and suggested an international syndicalist congress.

"[5] Likewise, its political counterpart, the Second International, was attacked by the British as a "body that exacts a pledge of parliamentarism and is composed of glib-tongued politicians who promise to do things for us, but cannot even if they wanted.

[7] The invitations were immediately received warmly by numerous syndicalists, including the Free Association of German Trade Unions (Freie Vereinigung deutscher Gewerkschaften in German, FVdG), Pierre Ramus's journal Wohlstand für Alle from Austria, the Central Organisation of the Workers of Sweden (SAC), the Spanish periodical Tierra y Libertad, the Italian Syndicalist Union (Unione Sindacale Italiana in Italian, USI), the Industrial Workers of the World (IWW) in the United States, and the Syndicalist League of North America.

The FVdG in Germany, for example, where the ISNTUC-affiliated Free Trade Unions would not allow a rival organization from the country to join, did not have this possibility.

The CGT wanted to preserve unity within the European labour movement, even with non-syndicalist groups, and was afraid affiliation with a syndicalist international would jeopardize its relations to the mainstream socialist unions.

Alceste De Ambris, a leader in the Italian USI, on the other hand argued that international secretariats like ISNTUC were useless.

Bowman, then ISEL's sole leader as Mann was in the United States on a speaking tour, announced the congress would take place from 27 September to 2 October at Holborn Hall in London.

In response, La Vie Ouvrière, the CGT's official organ, attacked both Cornelissen and De Ambris in a piece drafted by a number of leading French syndicalists, including Monatte, Jouhaux, Alphonse Merrheim, Alfred Rosmer, and Georges Dumoulin.

It claimed the uses of the congress, the exchange of information and mutual aid between national federations, were outweighed by the risk of deepening schisms within the European labour movement, especially if a formal international organization was to be founded.

At the time, the Irish Transport and General Workers' Union, which had syndicalist elements, was involved in the Dublin Lockout and the British were focused on supporting this struggle.

[16] The congress was attended by 38 delegates representing 65 organizations from Argentina, Austria, Belgium, Brazil, Cuba, France, Germany, Italy, the Netherlands, Poland, Spain, Sweden, and the United Kingdom[17] with a total membership between 220,000 and 250,000.

All major European national syndicalist union confederations, except for the French CGT, sent delegates: the German FVdG, the Dutch NAS, the Swedish SAC, and the Italian USI.

The Brazilian Regional Workers' Federation, unable to send a delegate for financial reasons, opted to be represented by Guy Bowman.

Additionally, the American Industrial Workers of the World (IWW) organizer George Swasey attended some of the sessions, though not as a delegate of his union.

He explained that the two most important tasks of the congress should be drafting a declaration of principles and to deciding upon how international cooperation between syndicalist groups would continue.

The Dutch delegates, on the other hand, argued that Wills' political involvement was irrelevant, as long as he was a syndicalist on economic and labour questions.

Wills, himself, claimed that he was not a politician, since a borough councilor's duties were strictly administrative, while insisting that he was a fervent opponent of parliamentary politics.

Support for De Ambris's position eventually ebbed and he gave in; the declaration that was finally unanimously accepted contained a number of references to the overthrow of the state.

As a solution, the congress "declares for the socialization of such property by constructing and developing our Trade Unions in such a way as to fit them for the administration of these means in the interest of the entire community."

However, the syndicalists felt "Trade Unions will only succeed when they cease to be divided by political and religious differences [and] by using Direct Action".

However, an Argentine delegate claimed De Ambris's numbers were wrong, stating that from South America alone, 600,000 would join a Syndicalist International.

Much like the CGT in the run-up to the congress, De Ambris was now worried about deepening the schism within Europe's labour movement and thereby weakening it.

He pointed to the CGT member unions at the meeting, saying they would be unable to go against their national and international affiliation, but would have no problems adhering to a committee of information.

Most delegates, however, felt the bureau could be seated neither in Paris, because of the CGT, nor in Berlin, the location of ISNTUC's headquarters, and therefore agreed on Amsterdam.

Its role would be to facilitate the exchange of information between the national groups, to cultivate syndicalist solidarity, and to organize future congresses.

It would publish the Bulletin international du mouvement syndicaliste, thus far edited by Cornelissen, and draw its revenue from the subscriptions to this periodical.

The German Die Einigkeit noted that the congress had accomplished the tasks set out in Fritz Kater's opening address.

Many syndicalists viewed the formation of the Bureau as the congress's biggest accomplishment, some even claiming that there was no real difference between it and an International.

The British Socialist Party's journal Justice labeled the declaration of principles "a strange mixture of Socialism and Anarchism", while the organ of the German Free Trade Unions claimed it "contains nothing but trite phrases".