sentences:  In contrast with the previous period of Romanian control, most cultural and educational rights of the Bulgarian minority were taken away which led to cases of armed resistance such as the Tatarbunary Uprising of 1924.The Molotov–Ribbentrop Pact of 1939 led to the June 1940 Soviet ultimatum, the invasion and annexation of Bessarabia by the Soviet Union.Although an officially accepted minority under Soviet rule, the local Bulgarians lost some features of their cultural identity.