After World War II Ukrainian Catholics came under the rule of Communist Poland and the hegemony of the Soviet Union. With only a few clergy invited to attend, a synod was convened in Lviv (Lvov), which revoked the Union of Brest. Officially all of the church property was transferred to the Russian Orthodox Church under the Moscow Patriarchate, Most of the Ukrainian Greek Catholic clergy went underground. This catacomb church was strongly supported by its diaspora in the Western Hemisphere. Emigration to the U.S. and Canada, which had begun in the 1870s, increased after World War II.