In the Governorate of Estonia, Estonians called for freedom of the press and assembly, for universal suffrage, and for national autonomy. On 29 October , the Russian army opened fire in a meeting on a street market in Tallinn in which about 8 000-10 000 people participated, killing 94 and injuring over 200. The October Manifesto was supported in Estonia and the Estonian flag was displayed publicly for the first time. Jaan Tõnisson used the new political freedoms to widen the rights of Estonians by establishing the first Estonian political party - National Progress Party. Another, more radical political organisation, the Estonian Social Democratic Workers' Union was founded as well. The moderate supporters of Tõnisson and the more radical supporters of Jaan Teemant could not agree about how to continue with the revolution, and only agreed that both wanted to limit the rights of Baltic Germans and to end Russification. The radical views were publicly welcomed and in December 1905, martial law was declared in Tallinn. A total of 160 manors were looted, resulting in ca. 400 workers and peasants being killed by the army. Estonian gains from the revolution were minimal, but the tense stability that prevailed between 1905 and 1917 allowed Estonians to advance the aspiration of national statehood.
Question: How many years did the Estonian revolution last?
Answer: 12