In 1920 and 1921, Russia witnessed a number of peasant uprisings against the government, sparked by local opposition to the requisitioning, but these were suppressed. Among the most significant was the Tambov Rebellion, which was put down by the Red Army. To aid the famine victims, Herbert Hoover, the President of the United States, established an American Relief Administration to distribute food. Lenin was suspicious of this aid, and had it closely monitored. Within the Communist Party itself there was dissent from both the Group of Democratic Centralism and the Workers' Opposition, both of whom criticised the Russian state for being too centralised and bureaucratic. The Workers' Opposition, who had connections to the state's official trade unions, also expressed the concern that the government had lost the trust of Russia's working class. The 'trade union discussion' preoccupied much of the party's focus in this period; Trotsky angered the Workers' Opposition by suggesting that the trade unions be eliminated, seeing them as superfluous in a "workers' state", but Lenin disagreed, believing it best to allow their continued existence, and most of the Bolsheviks eventually embraced this latter view. Seeking to deal with the problem of these dissenting factions, at the Tenth Party Congress in February 1921, Lenin brought about a ban on factional activity within the party, under pain of expulsion.