The uprising was ultimately crushed by the Russian authorities. Official reports indicated 151 civilian deaths  and 150 wounded; unofficial reports spoke of over 200 fatalities and between 800 and as many as 2,000 wounded. The Łódź uprising was neither the first nor the last disturbance in what has been described in Polish historiography as the revolution in the Kingdom of Poland —various protests and strikes occurred in major Polish cities under Russian control throughout the year—but it would be the most dramatic one. In September 1905, two PPS activists would assassinate Juliusz Karol Kunitzer, owner of the Heinzel & Kunitzer factory, known for his poor treatment of workers. Strikes in Łódź continued until mid-1906, when the large Russian military presence and mass layoffs of striking workers from the factories finally pacified the city. Even afterward, Łódź was not a peaceful city; in the years 1910-1914 it was the site of a radical, anarchist and socialist group Rewolucyjni Mściciele labeled as "the most extreme, terrorist group in the history of Poland". The uprising was reported in the international press and recognized by socialist and communist activists worldwide.

Based on the above article, answer a question. For how many years it was labeled as "the most extreme, terrorist group in the history of Poland'?
4