Introduction:
The Revolution of 1905 was a significant event in Russian history that marked the first time the autocratic rule of Tsar Nicholas II was seriously challenged. It was a period of widespread unrest and protests against the government, triggered by a combination of political, economic, and social factors. This revolution was a precursor to the larger and more successful Russian Revolution of 1917.

Factors leading to the Revolution:
1. Bloody Sunday: On January 9, 1905, a peaceful protest led by Father Georgy Gapon was brutally suppressed by the Imperial Guard in St. Petersburg. This event, known as Bloody Sunday, resulted in the death of hundreds of unarmed demonstrators and sparked outrage and further unrest among the population.

2. Condition of Workers: The working class in Russia faced harsh working conditions, low wages, long hours, and lack of basic rights. Industrialization had led to the growth of factories, but workers had limited representation and were often subjected to exploitation. This discontent among the workers played a significant role in fueling the revolution.

3. Russo-Japanese War: The Russo-Japanese War of 1904-1905 was a major factor in the Revolution. Russia suffered a series of military defeats, which exposed the weaknesses and inefficiencies of the autocratic regime. The war led to a loss of prestige for the Tsarist government and further fueled the discontent among the population.

4. October Manifesto: The October Manifesto, issued by Tsar Nicholas II in October 1905, was a response to the growing unrest and demands for political reform. It promised civil liberties, the establishment of a legislative assembly (the Duma), and an end to censorship. While the manifesto did lead to some concessions, it did not fully address the demands of the revolutionaries and failed to satisfy the growing desire for fundamental change.

Conclusion:
Among the factors mentioned, the October Manifesto was not a cause of the Revolution of 1905. Instead, it was a response by the Tsar to the ongoing unrest and a concession made in an attempt to quell the revolution. The other factors - Bloody Sunday, the condition of workers, and the Russo-Japanese War - played significant roles in fueling the revolution by creating widespread discontent, exposing the weaknesses of the autocratic regime, and undermining the authority and legitimacy of the Tsarist government.